The landlords protesting the bank’s SVR rise have submitted their case to the Office of Fair Trading, the Financial Conduct Authority and the Financial Ombudsman Service in the hope it will cost less than pursuing the bank through the courts.

The Law Department principal Justin Selig told Your Mortgage the regulators might have heard the Bank of Ireland’s story but were yet to hear the landlords’ side of the case: “We are just trying to pursue this avenue because it is the lowest cost option for the borrowers involved. If we have to go down a legal route, though, we will.”

He said the bank had breached regulations and the regulators needed to act as a result: “That is why these bodies exist – to protect the consumer.”

The OFT had said they would look at it and also recommended approaching the FCA, he added.

Landlord groups have rallied 100 affected borrowers to contest the Bank of Ireland’s decision to raise rates on certain residential and buy-to-let tracker mortgages on the basis the action is inherently unfair.

However, in April, it was revealed Financial Conduct Authority chief Martin Wheatley wrote to MPs describing the bank’s action as fair.

In a response to criticism, the Bank of Ireland has said the increase was permitted by a specific clause in the mortgage contracts.

It stated: “This change reflects the significant increase in the cost of funding these mortgages since 2008 and the need for banks to maintain greater levels of capital. This rate increase does not affect Post Office customers.”