Foreign national prisoners facing deportation have won permission to bring test case appeals against new laws aimed at removing them from the UK as quickly as possible.

The landmark human rights cases involve two convicted drug offenders who face removal - even though they have launched legal actions to block being deported.

They are the first to come before the Court of Appeal challenging the lawfulness of Home Secretary Theresa May's new "deport first, appeal later" regime.

Lord Dyson, Master of the Rolls, sitting with Lord Justice Underhill, gave the men permission to appeal, saying their cases raise issues of wide importance and should be heard by a three-judge court as soon as possible.

The challenges are being brought by Kevin Kinyanjui Kiarie, a Kenyan who came to the UK as a young child in 1997, and Courtney Aloysius Byndloss, a Jamaican father of at least seven children born in the UK.

Both have been told they must conduct their battles against removal respectively from Kenya and Jamaica.

They say the Home Secretary's powers to order out-of-country appeals violate their human rights on several grounds.

These include the disruption caused to family life and - in the Byndloss case - the harm a deportee's removal, even if only temporary, could cause to his children.

Lawyers for the men also point to the procedural difficulties in obtaining a fair appeal hearing in places far from the UK.

It is contended they will not have the benefit of legal aid and could face serious problems, including gaining access to video-link or internet facilities.

The appeal court ordered a stay on their deportations pending the outcome of their challenges. It is understood that deportations in other cases could also be halted pending a final ruling.

Lord Justice Underhill said: "It is clearly important that the court considers these recently-introduced provisions which make a significant difference to the way in which the secretary of state is able to deal with cases of deportation of foreign criminals."

The judge said other similar cases were "in the pipeline" and there had to be "an authoritative and early decision of this court for the guidance and tribunals who have to evaluate these provisions in the future".

The deportation powers under challenge were introduced by the Immigration Act 2014, which amended the Nationality, Immigration and Asylum Act 2002 by inserting a new section 94B.

The section allows the Home Secretary to certify that appeals against deportation are fit to take place out-of-country and there is no "real risk of serious irreversible harm" being caused to the appellant.

Previously deportation cases carried an automatic right of appeal in the UK, which led to criticism that the legal system could be used to delay deportations for years, with applicants lodging a string of appeals and requests for judicial review in the British courts.

Home Office figures show that more than 1,000 people have been removed under the tough new provisions since they came into force last year.

Kiarie, 21, is appealing against a decision of the Upper Tribunal (Immigration and Asylum Chamber) on March 6 this year refusing him permission to pursue a claim for judicial review in the UK after the Home Secretary certified his case under section 94B.

He claims that his removal from the UK would be contrary to his Article 8 "right to family life" under the European Convention on Human Rights.

Kiarie, who entered the UK as a dependent of his asylum-seeking mother and was given indefinite leave to remain, was convicted and fined in September 2013 of using a motor vehicle while uninsured, resisting or obstructing a police constable and failing to surrender to custody.

Convictions and jail sentences followed in 2014 for possession of heroin, cocaine, crack cocaine and cannabis. In July that year he was notified of his liability for deportation.

His lawyers argued before the Upper Tribunal that removing him to Kenya under section 94B would violate his Article 8 rights and deprive him of "fair and effective" involvement in his appeal against deportation.

They also accused the Home Secretary of failing to consider material factors, including whether Kiarie's removal would be contrary to her obligations under section 6 of the Human Rights Act 1988 not to act contrary to the human rights convention.

But the Upper Tribunal ruled that Mrs May was entitled to conclude that deportation would not cause him a real risk of serious irreversible harm, and there was no evidence that he would not be able to fully take part in his appeal from Kenya "with the assistance of family in the UK".

Byndloss, a father of seven - and possibly eight - children by three partners, applied for judicial review of his certification under section 94B at the High Court in Birmingham last December.

In May 2013 Byndloss was jailed for three years at Wolverhampton Crown Court for possessing Class A drugs with intent to supply and was described by the trial judge as playing "a significant role" in the drugs trade.

He also has convictions for violence but of "a relatively low order".

He was served with notice of liability to automatic deportation in June 2013, and a deportation order was signed in October 2014.

He applied to High Court judge Mr Justice Males for permission to seek judicial review on the grounds that being forced to appeal against the order out-of-country would be a "disproportionate interference" with his Article 8 rights to private and family life.

But the judge ruled his arguments were "entirely unjustified". The judge added that, even if his judicial review application was to succeed, the pressure on court time meant that a decision in an out-of-country appeal "could probably be given more quickly".

If his judicial review failed "he would still have the out-of-country appeal which would not, on this hypothesis, even get started for some months from today".