Conservative leadership contender Andrea Leadsom has come under further pressure to publish her tax returns after reports that a company with family links used a potential tax avoidance mechanism.
Gloucester Research Limited, owned by Leadsom's brother-in-law and run by her husband, had used an employee benefit trust (EBT) for four years, The Times first reported.
Although they are not illegal, EBTs were clamped down on by HMRC after concerns they were being used to avoid income tax and National Insurance contributions.
EBTs allow money or shares to be transferred into a trust, which are then paid to employees in the form of a long-term loan, or when they are retired or no longer a resident in the UK for tax purposes.
Gloucester Research donated over £70,000 to Leadsom between 2011-2012.
It is not clear whether Leadsom or her husband have benefited. A spokesperson for Leadsom said she had not known of the use of an EBT.
On Sunday Leadsom said she would only publish her tax returns if the made it down to the final two candidates in the Tory party election.
Under Conservative party election rules candidates with the least support are eliminated at each round of MPs voting, before the final two candidates make it to a ballot of party members.
Home secretary Theresa May remains the frontrunner, with more pledged MPs than the rest of the candidates combined.
It is expected that Liam Fox will be eliminated this evening, leaving Stephen Crabb and Michael Gove alongside May and Leadsom.