Chancellor Jeremy Hunt has asked the City watchdog to speed up a probe into whether people have had bank accounts closed due to their political views.
It follows a row over the closure of former UKIP leader Nigel Farage’s Coutts account.
Mr Hunt called on the Financial Conduct Authority (FCA) to “urgently investigate how widespread this practice is, and put a stop to it”.
The FCA said Mr Hunt’s request is “in line with our plans”.
It comes after Mr Farage obtained a report from Coutts which indicated his political views were considered as a factor in his account closure.
Mr Farage has launched a campaign against account closures which has received support from government ministers.
The FCA is already preparing to look into this, and banks also face government reforms over account closures.
Speaking to broadcasters, Mr Hunt said: “You can agree or disagree with Nigel Farage but everyone wants to be able to express their opinions.
“In today’s society, you need a bank account function and so a threat to be de-banked is a threat to your right to express your opinions.”
Mr Hunt said the FCA has the power to fine banks “very large sums of money if they find this practice is widespread”.
In a letter to the regulator on Thursday, Mr Hunt urged it to “urgently” speed up its planned review.
He asked it to investigate how many people had been affected and their characteristics.
He also also wanted the regulator to find out why the banks had taken these decisions, what monitoring and enforcement action the FCA had taken, and what action customers themselves could take.
FCA chief executive Nikhil Rathi said Mr Hunt’s request was “in line with our plans” and the FCA “will provide an initial assessment by mid-September”.
Mr Farage tweeted: “The Chancellor has written to the FCA about my case and the issue of de-banking. Thank you Jeremy Hunt.”
The ex-MEP this week said Coutts has offered to reinstate his personal and business accounts, while he wants compensation from the private bank.
NatWest has announced an independent review, with lawyers looking at the closure of Mr Farage’s account and other instances of customers losing Coutts accounts.
Dame Alison Rose, chief executive of NatWest Group, which owns Coutts, quit after saying she had made a “serious error of judgment” in speaking to a BBC journalist about Mr Farage’s Coutts account.
The boss of Coutts, Peter Flavel, also quit due to the row.
The BBC had initially reported Mr Farage’s account was closed because he no longer met the wealth threshold for Coutts, citing a source familiar with the matter.
