Labour has suspended seven MPs who voted for an SNP amendment calling for the two-child benefit cap to be scrapped.

According to reports, the rebels, including former Shadow Chancellor John McDonnell, will lose the whip for six months.

The amendment to a motion on the King’s Speech failed by 363 votes to 103, giving Sir Keir Starmer a majority of 260.

All but one of Scottish Labour’s 37 MPs voted with the government.

Katrina Murray, the new member for Cumbernauld and Kilsyth, was one of 42 MPs who did not vote either for or against the amendment.

The two child  cap was introduced by George Osborne on April 5, 2017 and prevents parents from claiming child tax credit or universal credit for a third and any subsequent child, born after that date.

However, there is an exemption for families where a third child is the result of “non-consensual conception.”

According to the Institute for Fiscal Studies, it currently affects two million children.

When fully rolled out, the cap will affect one in five children, rising to 38% of those in the poorest fifth of households, the IFS research found.

Labour has long said that they would, eventually, like to remove the cap but the state of the public finances means they cannot currently afford to do so.

The CPAG estimates it would cost £1.7 billion per year, but the government says it is more like £3bn.

In a bid to head off a larger revolt, ministers told backbenchers on Monday that they would consider ditching the “cruel” policy.

The SNP motion calling for the cap to be scrapped was backed by the Lib Dems, Plaid Cymru, the Green Party and other MPs, including former Labour leader Jeremy Corbyn – who is now an independent.

Along with Mr McDonnell, Labour’s Apsana Begum, Richard Burgon, Ian Byrne, Imran Hussain, Rebecca Long-Bailey, and Zarah Sultana all voted for the amendment.

The SNP's Westminster Leader, Stephen Flynn, said Labour had made a “political choice” not to lift “thousands of children out of poverty.”

He said his party will "campaign vigorously for the cap to be abolished at the earliest opportunity."

"The Labour government has a moral duty to go much further and faster to tackle child poverty. Scrapping the cap is the bare minimum we should expect.”

Earlier in the day, Labour’s Work and Pensions Secretary, Liz Kendall said driving down child poverty was a “real priority for this Government”.

Asked if that meant abolishing the cap, she told Times Radio that Labour was elected “on the promise that we would only make spending commitments that we know we can keep”.

“I’m not into a wink and a nudge politics,” she said.

“I’m not going to look constituents in the face and tell them I’m going to do something without actually having done the sums, figuring out how I’m going to pay for it, figuring out how we transform opportunity for those children, not just in terms of their household income, which is essential, but about having sustained improvements to helping people get work and get on in work, more childcare, early years support, sorting out the dire state of people’s housing.

“It’s got to be part of a much bigger approach.”