Channel 4’s Dispatches programme is set to air tonight with claims that complaints were handled by FOS officials who had been insufficiently trained and had to use internet search engines to find out what the products were.

Chartered Financial Planner Martin Bamford, MD of Informed Choice in Surrey, said: “The Financial Ombudsman Service has serious questions to answer. This investigation points to unfair treatment of customers and advisers. Time for FOS to publish the qualifications of their adjudicators.

“I'll be writing to my MP to call for a full inquiry into these issues and reform of what increasingly appears to be a system unable to deliver fair results for consumers or businesses.”

The Times reported that the documentary found investigators at the FOS had been “churning” out decisions as “they scrambled to meet targets, one said”.

A Times report read: “Speaking to an undercover reporter from Dispatches, the Channel 4 programme, the employee said it was “not feasible” to handle all the claims.

Asked whether it was easier to rule against complainants, they were heard to reply: “Yeah, because you just need to make one call to the consumer, rather than trying to persuade the business, which is actually a lot harder.”

“Another insider was recorded saying that they had ‘just taken a chance and just slung stuff through, with any old decision.’ They added that ‘colleagues also admit they ‘fling it through’. This usually means in favour of the bank. It just makes it easier.”

Financial Planning Today has contacted the FOS about the claims and asked if it would be launching an investigation and whether it had taken any action so far.

The FOS replied with a statement, which read: "Our role is to investigate disputes between financial businesses and their customers - making impartial decisions based on what's fair and reasonable in each individual case. We take our work very seriously, making difficult judgement calls that affect people's lives.

"We haven’t seen the programme yet, but the impression given is clearly not representative of us at our best and we will be taking any concerns raised in it seriously. Our people are committed to doing the right thing and we always want to know how we can improve."

The documentary entitled 'Undercover: Who is policing your bank', will be shown on Channel 4 tonight at 8pm.

• Editor's note: Story updated with FOS response at 10.52am.