An MP who accused a leading campaigner of being an “outed Holocaust denier” has apologised for the slur and agreed to pay £10,000 in compensation.

Natalie McGarry, the Scottish National Party MP for Glasgow East, also called Scotland in Union director Alastair Cameron an “internet troll” in a tweet posted on March 6.

As part of the agreement with Mr Cameron, she tweeted today that she had “made a serious mistake and accept there is no truth to those statements and apologise unreservedly to Mr Cameron for any distress caused”.

The apology was initially hidden from public sight after Ms McGarry made her account private, but was made public after a tweet from Mr Cameron warned her to take action, “or regrettably there may be further [actions] from my solicitor”.

The £10,000 will be split between three organisations: veterans’ mental health charity Combat Stress, genocide-prevention NGO Aegis Trust and Lumos, a charity started by Harry Potter author JK Rowling to help children.

Ms Rowling had suggested she may sue Ms McGarry following a Twitter spat in which the MP falsely accused her of defending “abusive misogynist trolls”.

Ms McGarry was elected for the SNP in last year’s general election, but now sits as an independent.

She resigned the party whip last November after police opened an investigation into the accounts of the Women for Independence group, which she founded.