Labour and the Conservatives are coming under increasing pressure to end the two-child cap on benefits paid to families with children.

Low-income parents are currently denied key benefits, including Universal Credit, for their third and any subsequent children born from April 2017.

Research by the Institute for Fiscal Studies (IFS) finds that when fully rolled out, the policy will affect one in five children, costing families an average of £4,300 a year.

The policy already applies to about 2…