LONDON - Former UK prime minister Theresa May has earned over £2.5 million (S$4 million) on top of her official salary from outside engagements since the last general election, the most of any UK member of Parliament, according to an investigation by Sky News reports.

Overall, parliamentarians earned £17.1 million extra since late 2019 on top of their individual £84,144 annual salaries. Two thirds of the larger amount went to just 20 MPs and of those, 17 were from the ruling Conservative party, two from Labour and one was from Sinn Fein.

Sky spent seven months compiling a database of the earnings based on regulatory filings by the MPs and posted a search tool to allow people to see how much their local MPs earned and who was paying them. 

Ms Theresa May’s outside interests included a payment of £107,600 for a speech in Saudi Arabia, a country she banned officials from visiting when she was Prime Minister after the killing of Jamal Khashoggi.

Former Prime Minister Boris Johnson ranked third, but could soon overtake May as the top earner. He took in more than £1 million since stepping down last year. Most of his earnings came from four speeches in October and November. One of these paid him at a rate of £32,500 per hour, Sky said.

Two Labour MPs were among the top 20 earners even though their party leader Keir Starmer has previously called for second jobs to be banned. 

“I think we should get rid of second jobs with some exceptions,” Mr Starmer told Sky News’ Sophy Ridge on Sunday. “I am open to a discussion on this. I think the rules should be stricter.”

The revelations come a little over a year after Conservative MP Owen Paterson resigned amid a lobbying scandal. The controversy prompted a review of the rules and further limits are due to be placed on the sort of work lawmakers can engage in.