An open letter demanding the resignation of Labour’s defence spokesperson Nia Griffith has reached almost 1,500 signatures, after the opposition frontbencher tweeted apparently in support of government proposals to grant veterans immunity from prosecution.

Penny Mordaunt, the new Defence Secretary, recently revealed plans to introduce an amnesty for alleged offences committed by British soldiers in the course of duty over 10 years ago. The cabinet is divided over whether this should cover soldiers who served during the Troubles in Northern Ireland.

Many Labour members on the left, particularly those interested in the anti-imperialism and anti-militarism traditionally espoused by Jeremy Corbyn, expressed strong opposition to the suggestion when the six-day-old tweet by Griffith gained traction last night.

Glad to hear this from the new Defence Sec. The Tories made a commitment to deal with this back in 2017 and it‘s shameful that no action has been taken. Labour will support any proposals that are effective and fair and I look forward to working with @PennyMordaunt on this. https://t.co/2dn2pBDzbr — Nia Griffith MP (@NiaGriffithMP) May 9, 2019

An open letter written by two Scottish Labour members, Ewan Gibbs and Michael Muir, criticises the position expressed by Griffith, which it says “legitimates the most reactionary elements of British society”.

Addressed to Corbyn, it calls on the national executive committee (NEC) to “discuss and clarify the party’s stance” and demands that the party leadership take action if Griffith refuses to resign.

It is understood that a reference to the NEC, a body that usually deals with the application of party rules rather than policy-making, was included in the letter as a way of encouraging NEC members to ask Corbyn whether Griffith’s stance accurately reflects Labour policy.

The online letter was promoted by NEC youth rep Lara McNeill, and has been signed by high-profile activists including Momentum chair Jon Lansman, NEC member Huda Elmi and Young Labour’s Marcus Barnett.

Although the names have not been updated at the time of writing, LabourList has seen that the letter has attracted almost 1,500 signatures. Most so far are from young Labour members.

Young Labour, London Young Labour and Scottish Young Labour have all released statements calling for Griffith’s suspension or resignation from the shadow cabinet.

Update, 1.10pm. Momentum has called on Griffith to “retract her statement”:

We can’t just give soldiers a blank cheque to commit war crimes. It would dishonour all those soldiers and civilians who have been killed in war and we have to hold our military to the highest standards. @NiaGriffithMP was totally wrong and should retract her statement. — Momentum (@PeoplesMomentum) May 16, 2019

LabourList has requested comment from the Labour press office but none has been offered at this time.