The Holocaust survivor who forced the government to accept child refugees is demanding they keep their promise after they quietly scrapped a pledge to help thousands of lone asylum seekers under the age of 15.

Lord Alf Dubs said he will challenge the "bitterly disappointing" termination of his amendment to the immigration act, which forced Theresa May to let in the most vulnerable people from countries such as Syria.

He intends to file a Private Notice Question in the House of Lords today, and says Labour MP Yvette Cooper is to raise the "shabby" move in the House of Commons.

Just hours before the final vote on the triggering of Article 50, the government announced it would allow only 350 unaccompanied asylum seeking children to come to the UK under the scheme which was expected to help thousands, in a statement that Lord Dubs described as "confusing" and "hidden".

“It’s been sandwiched between PMQs and all these votes on Brexit – what a way of hiding an announcement,” he said, telling the Independent he had not been notified of the decision to end his amendment in advance, and believed the government had tried to sneak it through without anyone noticing.

He added that he had never heard the 350 children figure before. “Up to lunch time [on Wednesday] I was under the impression there was no cap,” he said.

The statement from Immigration Minister Robert Goodwill said local authorities indicated they “have capacity for around 400 unaccompanied asylum-seeking children until the end of this financial year” — 50 of those spaces have been allocated for delayed family reunion cases — and said the country should be “proud” of its contribution to finding homes for refugees.

But the new cap on Dubs children is thousands short of the figure suggested by government sources last year, and nobody outside of the Home Office had heard it before the shock statement on Wednesday.

“We knew 200 had come because they’ve been saying so,” Lord Dubs said.

“But the 350... the extra 150 has come from God knows where, they’ve just cooked it up... It's entirely new.”

He added: “They’ve [the government] recently said they would accept the letter and spirit of the amendment but they are manifestly not doing that.

"I think they’re using it as an excuse that local authorities don’t want to step up to the mark, and I think it is quite clear from the evidence that we have that local authorities would respond if asked.“

On Wednesday, Liberal Democrat leader Tim Farron called the decision “a betrayal of British values”.

“Last May, MPs from all parties condemned the Government’s inaction on child refugees in Europe, and voted overwhelmingly to offer help to the thousands of unaccompanied kids who were stranded without their families backed by huge public support,” Mr Farron said.

“Instead, the Government has done the bare minimum, helping only a tiny number of youngsters and appearing to end the programme while thousands still suffer. At the end of December last year the Government had failed to bring a single child refugee to the UK under the Dubs scheme from Greece or Italy where many of these children are trapped.”

Ministers introduced the programme last year after coming under intense pressure to give sanctuary to lone children stranded on the continent.

Calls for the measure were spearheaded by Lord Dubs, who himself came to the UK as a child fleeing the Nazis, whose amendment to the Immigration Act requires the Government to “make arrangements to relocate to the UK and support a specified number of unaccompanied refugee children from other countries in Europe”.

The legislation did not specify a figure, and campaigners had hoped that as many as 3,000 children would benefit from the scheme.

“I never argued that we should take them all,” said Lord Dubs, “I argued that we should take our share.”

He added: “I was in Greece a few weeks ago, the situation was dire, I think it is sort of arbitrary to say we’ll take 350 and that’s it and there are some very vulnerable children who are going to be left there.”

Judith Dennis, Policy Manager at the Refugee Council said: “The Government’s job is far from done; the global refugee crisis hasn’t gone away and if anything it’s getting worse.

“The UK needs to step up rather than step back and ensure that we pull our weight by offering refuge to more vulnerable people and enabling more refugees to reunite with their families here.”

In a written ministerial statement, Mr Goodwill said more than 900 unaccompanied asylum-seeking children were transferred to the UK from Europe in total last year.

This included more than 750 from France as part of Britain’s support for the clearance of the Calais jungle.

More than 200 of those children met the criteria for the Dubs route, while the remainder were transferred under an accelerated process based on, but operated outside of, the Dublin Regulation covering family reunion cases.

Mr Goodwill said: “The UK can be proud of its record of helping refugee children and I can today announce, in accordance with Section 67 of the Immigration Act, that the Government will transfer the specified number of 350 children pursuant to that section, who reasonably meet the intention and spirit behind the provision.

“This number includes over 200 children already transferred under Section 67 from France. It does not include children transferred to UK where they have close family here.

“We will announce in due course the basis on which further children will be transferred from Europe to the UK under Section 67 of the Immigration Act to the specified number.”

Calais Refugee Children arrive in UK Show all 9 1 /9 Calais Refugee Children arrive in UK Calais Refugee Children arrive in UK A coach carrying the first group of unaccompanied minors from the Jungle migrant camp in Calais to be brought to Britain arrives at an immigration centre in Croydon, south London Reuters Calais Refugee Children arrive in UK A Catholic priest chats to Muslim Imans as they wait for the arrival of the coach carrying the first group of unaccompanied minors from the Jungle migrant camp in Calais to be brought to Britain arrives at an immigration centre in Croydon, south London Reuters Calais Refugee Children arrive in UK Fourteen migrant children from the 'Jungle Camp' in Calais are due to arrive in the UK today to be reunited with relatives Getty Calais Refugee Children arrive in UK Young men are escorted after stepping off a coach at the Home Offices Lunar House Getty Calais Refugee Children arrive in UK A boy is escorted after stepping off a coach at the Home Offices Lunar House after arriving from the Calais 'Jungle Camp' Getty Calais Refugee Children arrive in UK UK Border Force staff escort the first group of unaccompanied minors from the Jungle migrant camp in Calais to be brought to Britain as they arrive at an immigration centre in Croydon, south London Reuters Calais Refugee Children arrive in UK A young boy arrives on a coach at the Home Offices Lunar House after leaving the Calais 'Jungle Camp.' Fourteen migrant children from the 'Jungle Camp' in Calais are due to arrive in the UK today to be reunited with relatives Getty Calais Refugee Children arrive in UK British former Archbishop of Canterbury Rowan Williams, center, flanked by Bethany Gardiner-Smith, left, from the Citizens UK charity and Bishop of Croydon Jonathan Clark speaks to the media about the 14 migrant children who will be resettled in the UK, outside Croydon Minster church in Croydon, south London AP Calais Refugee Children arrive in UK Asif Khan whose brother Aimal Khan was one of fourteen migrant children who arrived in the UK, speaks to the media outside Lunar House in Croydon, south London. The 25-year-old chef has been living in the UK for 11 years, having fled Afghanistan himself. His brother Aimal Khan, 14, also from Afghanistan, had been stranded in the Jungle for six months PA

The Home Office minister went on: “As required by the legislation, we have consulted with local authorities on their capacity to care for and support unaccompanied asylum-seeking children before arriving at this number.

“Local authorities told us they have capacity for around 400 unaccompanied asylum-seeking children until the end of this financial year.

“We estimate that at least 50 of the family reunion cases transferred from France as part of the Calais clearance will require a local authority placement in cases where the family reunion does not work out.