The former Archbishop of Canterbury has clashed with prominent Catholic MPs over the opening of new Catholic schools. Lord Williams co-signed a letter to the Daily Telegraph attacking the plans to lift a 50 per cent cap on the number of pupils a new school can select on the grounds of faith. The letter, also signed by God Delusion author Richard Dawkins among others, said it was “difficult to bring to mind a more divisive policy, or more deleterious to social cohesion”. Last week five Catholic MPs – Jacob Rees-Mogg, Sir Edward Leigh, Sir Bill Cash and Martin Vickers – wrote their own letter to the Telegraph, rejecting the argument as “illogical”. If the cap were lifted, dozens of new Catholic schools would be expected to open. The Church has not opened any free schools since the cap was introduced. That is because if a school is oversubscribed it would be forced to turn away pupils because of their Catholic faith – which bishops say would violate canon law. The Conservative manifesto promised to remove the cap. A petition signed by 18,000 Catholics urged the Government to honour its promise. The joint letter backed by Lord Williams said removing the cap “allows schools to label children at the start of their lives with certain beliefs and then divide them up on that basis”. It said the education system must not “highlight and entrench differences” but “emphasise the common values that we all share”. In their reply, Catholic MPs pointed out that existing Catholic schools were already a model of diversity, educating more than 26,000 Muslims. “To argue that the operator of the most diverse existing schools cannot be allowed to open new ones for fears they will not be diverse is entirely illogical,” the MPs said.