British firms could be left with £105 billion of unsustainable debt as coronavirus continues to eat into economic performance, one of the country's top financial lobby groups has warned.

Businesses will need major help if they are to get back on their feet after the Covid-19 crisis is over, TheCityUK said.

In a letter to Bank of England Governor Andrew Bailey, the group's chairman, Sir Adrian Montague, warned that business will be "seriously affected" by the pandemic in the long term.

"In the short term the financial impact on businesses, large and small, is serious and profound," said Sir Adrian, who is also the chairman of insurance group Aviva.

He warned that businesses will need "full-scale recapitalisation" to alleviate an employment hit and keep up investment at the levels needed to help the economy.

TheCityUK has estimated that private non-financial corporations held £90 billion to £105 billion in unsustainable debt by March 2021.

The Government's coronavirus interruption loan schemes (CBILS and CLBILS) could contribute between £10 billion and £20 billion of this, the trade body found.

Company bosses are likely to have to raise new money from equity, or restructure their debts as a result, Sir Adrian warned.

It means a lot of new capital will have to be pumped into businesses to help them stay afloat.

TheCityUK chief executive Miles Celic said: "The economic lockdown created by the pandemic has required unprecedented interventions. Businesses have been put into suspended animation until they can safely reopen.

"This was absolutely the right thing to do, but it means the job is not yet done. The economy will need to be reawakened as part of its process of recovery.

"Our industry is determined to play its part in getting the country back on its feet. Working at a pace and with real determination, firms across the industry are collaborating to identify a financially viable pathway to recovery and a return to long-term growth for UK businesses."