Jeremy Corbyn told MPs this morning that hundreds of private jets have been stashed on the Isle of Man as part of a tax avoidance scheme.
During today's Prime Minister's Questions, Corbyn said 957 jets have been imported onto the island. He said the number of aircraft "seems a bit excessive for any island anywhere".
"So can the Prime Minister assure the House that HMRC investigates these new allegations diligently?" Corbyn said.
The Labour leader was referring to allegations made by the International Consortium of Investigative Journalists (ICIJ).
However, the Isle of Man government said it had already asked Westminster to conduct a review of its practices in this area.
The Isle of Man started an internal review last week on the imports of business jets. However, the Isle of Man's chief minister Howard Quayle has said there is no evidence of wrongdoing with regards to VAT payments. The review is expected to be completed in 2018.
The revelations from the ICIJ come after a data leak from law firm Appleby, which operates in locations such as Jersey, the Isle of Man, the Cayman Islands and Bermuda.
Corbyn at PMQs said Appleby was Bermuda-based but last night the Bermuda government hit back at the Labour leader for implying it was allowing tax avoiders to operate within its territory, saying: "Bermuda is a recognised leader in international tax compliance and tax transparency with 114 tax treaty partners."
May said the government had introduced more than 100 tax avoidance measures, adding that the Conservatives had raised £160bn through compliance measures since 2010. She said all cases referred to HMRC are taken very seriously.