The election watchdog faces calls to investigate Facebook ads about the government’s controversial Towns Fund targeted at key marginal seats in 2019.

HuffPost UK revealed last year that the government paid for more than 20 ads in swing seats trumpeting £25m investment in “your town”.

The messages, which could still be found on the site when MPs backed an early general election in October, all appeared to be specifically targeted at areas where the sitting MP had a majority below 5,000, such as Milton Keynes, Morley and Workington. 

Facebook pulled the ads after they were highlighted, saying they were not correctly labelled.

“Ads about social issues, elections or politics that appear on our platforms should include a disclaimer provided by advertisers,” a spokesman for the site said. 

Now, Labour has written to the Electoral Commission asking the body to “investigate the circumstances of this alleged misuse of public funds”. 

It follows fresh questions for communities secretary Robert Jenrick, whose Ministry of Housing, Communities and Local Government runs the scheme, who has repeatedly been called to parliament to answer questions about whether the fund was used to “funnel” cash to target seats.

The government has insisted the process “comprehensive, robust and fair” but a highly critical report by the Public Accounts Committee said the fund was “not impartial” and ministers ignored officials’ advice. 

Meg Hillier, chair of the committee, said the system gave “every appearance of having been politically motivated”.

MPs also said some towns were picked by ministers, including Jenrick’s own Newark constituency, “despite being identified by officials as the very lowest priority”.

Cat Smith, shadow minister, has written to Bob Posner, chief executive of the Electoral Commission.

In the letter, seen by HuffPost UK, she says: “On the cusp of a general election, this sort of targeted advertising is clearly inappropriate when paid for out of the public purse.

“This is a clear case of public money being used to advance the political interest of the Conservative Party.

“In light of the recent Towns Fund scandal, we know that taxpayers’ money has been used to benefit the Conservative Party.”

She adds: “In a time of increasing disregard for democratic processes and norms worldwide, it is vital that the UK government is held to the highest democratic standards and acts both legally and transparently.

“I would urge the Electoral Commission to investigate the circumstances of this alleged misuse of public funds, and to report on its findings publicly as soon as possible.

“Ministers must answer these questions and reassure the public that taxpayers’ cash is not being spent by the Conservatives for their own gain.”

When approached the government about the Facebook ads last year, a spokesman said “all towns selected were chosen according to the same selection methodology, including analysis of deprivation, productivity, economy resilience and investment opportunities”.

It said that the ad campaign ended before the official election campaign started, even though posts could still be found.

They said: “The My Town campaign began on 25 October and has now ended in the run up to the pre-election period. While the posts are still be present on Facebook, they are no longer being promoted as the paid-for campaign has ended.”

They added that “the ‘My Town’ campaign was designed and launched before the general election was called”. 

“The campaign was targeted at all the places selected to bid for the Towns Fund – not at a limited number or to specific areas as suggested,” the spokesman said, adding that the posts were no longer promoted but could be found online.  

“This approach was designed and recommended by officials in the department.”