The first small boat migrant has been sent back to France under the new ‘one in, one out’ returns deal, Home Office sources have confirmed.

The Indian man was flown from London to Paris this morning, it is understood. 

A further migrant is due to be deported on another flight later today.

After three days of failed attempts, the Home Office faced challenges in making the initial deportation under the agreement signed in July by Prime Minister Sir Keir Starmer and French President Emmanuel Macron.

A prominent legal challenge on Tuesday forced the government to halt efforts to deport a 25-year-old Eritrean man who was supposed to be on a flight at 9am yesterday.

An Air France Airbus jet pictured on the apron at London’s Heathrow airport yesterday

The case led Home Secretary Mahmood to condemn small boat migrants who lodge last-minute legal challenges.

She said it ‘made a mockery of our laws’ when they tried to dodge deportation by claiming they were victims of ‘modern slavery’.

However, Tory counterpart Chris Philp criticized Labour, claiming they have ignored how immigration laws function and lack the drive for real change.

Philp expressed concern that Prime Minister Sir Keir Starmer and Attorney General Lord Hermer, both former human rights attorneys, will not support meaningful reforms to the human rights and other laws that are used to block deportations.

Ms Mahmood said last night: ‘Last minute attempts to frustrate a removal are intolerable, and I will fight them at every step.

‘The sudden last-minute claims of being a modern slave, never previously mentioned, undermine our laws and this nation’s generosity.’

Home Secretary Shabana Mahmood has condemned small noat migrants who lodge ‘vexatious’ last-minute legal challenges

She added: ‘I will fight to end vexatious, last-minute claims.

‘I will robustly defend the British public’s priorities in any court. And I will do whatever it takes to secure our border.’

Her remarks were the strongest recognition yet by a Labour minister of how legal strategies are used to hinder deportation efforts.

But since the new returns deal with France was announced the Government has been repeatedly warned it was vulnerable to human rights and modern slavery claims.

On July 10, the day the policy was launched, the Daily Mail questioned senior Home Office figures about the possibility of legal challenges – but officials refused to speculate on how they would be handled.

This week’s High Court ruling on the unnamed Eritrean migrant paved the way for copycat claims by others at risk of deportation under the scheme.

About half of the 92 migrants reported to be in Home Office custody are expected to bring claims, legal sources said, by deploying similar human rights and ‘modern slavery’ grounds.

It could leave the majority of cases lined up for the returns deal in legal limbo for months.

The day after his arrival in Britain on August 12 the Eritrean migrant said he had not been exploited on his way here.

But soon after he submitted a modern slavery claim alleging he had been forced to work unpaid in Libya while on his way to Europe.

The High Court granted an injunction barring his removal for 14 days while the modern slavery application is scrutinised.

The Home Office will appeal, sources said, in a bid to have the length of the injunction reduced so the Eritrean man can be deported.

The Home Secretary has also launched an urgent review of the Modern Slavery Act to assess where it is currently open to misuse, they added.

The Prime Minister – who scrapped the Tories’ Rwanda asylum deal as one of his first acts in office – has previously insisted Britain will never leave the European Convention on Human Rights, which many migrants deploy in their legal claims.

Before he entered politics, barrister Sir Keir edited a legal manual on how to interpret the new human rights laws shortly after they came into force, describing how they had ‘enormous potential’ and represented a ‘new way of thinking’ about the law.

Since the ‘one in, one out’ deal came into force on August 7, more than 5,400 small boat migrants have reached Britain.

The delays – and the prospect of more challenges ending up in court – have placed huge pressure on the Government as it struggles to tackle the Channel crisis.

So far this year 31,026 migrants have arrived, up 38 per cent on the same period last year.

Former home secretary Yvette Cooper was moved sideways to the Foreign Office in this month’s reshuffle after she failed to make progress.