Some senior Tories have accused MPs, many of which are their colleagues, of being “plain wrong” for earning money as landlords of properties in London, while also claiming taxpayers’ cash to rent separate homes in the capital.

At least 15 MPs have been exposed for each letting out a home in London for more than £10,000 a year while renting another property on expenses.

It has been revealed that the MPs, of whom 13 are Conservatives and three are ministers, are claiming up to £22,920 a year for rent payments.

Although there is no suggestion the MPs letting properties have broken any rules, it is viewed upon by some as immoral, and will now be “properly looked into by the [Parliamentary] Commissioner for Standards”, according to prime minister Boris Johnson.

Among those found to be exploiting the loophole is the former attorney general Sir Geoffrey Cox, who is claiming £22,000 a year after he moved into a rented property.

At the same time, his declaration in the Register of Members’ Interests showed that from November 2017 he was collecting more than £10,000 a year renting out a residential property in London.

The move was heavily criticised by veteran backbencher Sir Roger Gale, who branded the situation as “plain wrong”.

He told the Radio Times: “It’s maybe within the regulations, but it’s wholly against the spirit of what is happening.

“The intention was that you have to have – and you do have to have – a second base. If you’re a member of parliament, there’s no doubt about that. You’ve got to go and sleep somewhere.

“We don’t sit late at night as we used to, that’s certainly true. But nevertheless, most members of parliament from most parts of the country can’t get home at night. So you have to have somewhere to stay.”

According to The Times, many MPs believe they are pushed into claiming for rent paid on a London rental property to live in, which is permitted under Independent Parliamentary Standards Authority (Ipsa) rules because as members of parliament they are not allowed to claim mortgage interest payments as expenses.

Ipsa has said that while there could be a “perception of personal gain if an MP receives rental income while living in a parliamentary-funded flat”, but it decided to continue to allow MPs to claim for rental costs even if they own a property in London.

But Conservative Sir Peter Bottomley, the longest-serving MP in the Commons, told the Guardian the current rules had created a loophole which needed to be dealt with by all political parties working together.

Several Tory sources told the press over the weekend that they are angry over the actions of some of their colleagues, which they believe is resulting in all MPs being associated with the accusations of sleaze.