Campaigners will challenge the government's handling of the arrival of unaccompanied child refugees from Europe, at a High Court hearing later.
Campaigners say ministers have not worked with local councils to find enough places for vulnerable children.
Separately, the daughter of the man called "Britain's Schindler" has criticised the ending of the "Dubs amendment" child refugee scheme.
Ministers argue the arrangement is "a pull" for children and traffickers.
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On Wednesday, the government ended the Dubs amendment scheme, designed by the Labour peer and former child refugee, Lord Dubs.
The amendment, which was attached to the Immigration Act last year, required the Home Office to allow some of the most vulnerable unaccompanied children stranded in Europe into the UK.
However, refugee groups and charities have previously accused the government of dragging its feet on the issue.
The High Court case – which began before the government's announcement on Wednesday – argues that ministers have failed to work hard enough to find sufficient places for the children.
The court is expected to reserve its judgement until a later date.
Barbara Winton, daughter of Sir Nicholas Winton – who helped save hundreds of children from the Nazis in World War Two – called on the prime minister to reinstate the Dubs amendment.
In a letter to Theresa May, she said her father said the UK had "a responsibility to offer sanctuary those fleeing persecution".
"'If it's not impossible', he used to say, 'then surely something could and something must be done'," she wrote.
She called on prime minister to "remember" the words she used at a memorial to Sir Nicholas, when Mrs May said she hoped his life would "encourage us to do the right thing".
"As the world once again teeters on the edge of dark times, I ask you to remember those words," she added.
Ministers said 350 children would have arrived under the scheme by the time it ends in March, but there were fears it encouraged people traffickers.
Lord Dubs and his supporters have suggested the UK could help 3,000 of the most vulnerable.
On Thursday, church leaders, charities, MPs and peers also condemned the decision to close the scheme.
'No good reason'
The Archbishop of Canterbury Justin Welby said he was "saddened and shocked" at the government's decision to limit the number to 350, saying he hoped ministers would reconsider the decision.
Meanwhile, Lord Dubs said: "I believe in arbitrarily closing down the scheme, without any good reason for doing so, the government is in breach of its own commitments."
Home Secretary Amber Rudd defended the approach to the Dubs scheme – saying UK and French authorities feared it had provided opportunities for people-traffickers.
Speaking in the Commons, she said: "I am clear that when working with my French counterparts they do not want us to indefinitely continue to accept children under the Dubs amendment because they specify, and I agree with them, that it acts as a draw.
"It acts as a pull. It encourages the people traffickers."
The Home Office has insisted it is not giving up on vulnerable children and youngsters will continue to arrive from around the world through other resettlement schemes and the asylum system.