A Labour MP broke parliamentary rules by using House of Commons stationery for political campaigning on Brexit, a watchdog has found.
The parliamentary standards commissioner said Dr Rosina Allin-Khan, MP for Tooting, had broken the rules three times in three years.
She has been told to apologise and reimburse the full £1,142.52 cost of the stationery.
Under Commons rules MPs are only allowed to use official Commons letterheads for their business as an MP, with a strict ban on using official parliamentary resources for campaigning.
But the Commissioner found that a batch of 1,624 letters about Brexit to constituents sent on 2 November 2019 just before the general election amounted to political campaigning.
The watchdog said the incident saw the MP using "public resources to highlight to a group of voters her position and record on an issue that was one of the key themes of the imminent election".
The communication "contained an important personal campaign message, which...had the effect of seeking to support Dr Allin-Khan's return to office".
Given the incident was the third breach of rules, the committee said "any further breach of the Code of Conduct by Dr Allin-Khan, where there is evidence of a lack of attention to the rules of the House, might call for a more serious sanction".
A spokesperson for the MP said she "fully accepts the committee's recommendations", already offered to reimburse the costs of the stationery, had apologised, had taken steps to "ensure this does not happen again".