OIL company executives found by European Commission investigators to have manipulated petrol prices should be jailed, MPs have insisted as the UK Government warned that, in such circumstances, the culprits must face the full force of the law.

However, backbenchers calling for any fines – likely to run into billions of pounds – to be handed back to the public were disappointed as Ed Davey, the Energy Secretary, pointed out under EU law this could not happen.

On Tuesday, it was revealed the offices of BP, Royal Dutch Shell, Norway's Statoil and the Platts pricing agency were raided by commission officials looking at claims of price-fixing of oil. Some of the offices were in London.

In an emergency statement, the Secretary of State said the Coalition was deeply concerned by the allegations that for many years British motorists may have been paying more to fill up their cars than they need have.

Stressing how MPs should "not jump the gun" and allow the cross-border probes by the commission to run their course, Mr Davey, nonetheless, said: "If it turns out to be the case that hard-pressed motorists and consumers have been hit in the pocket by manipulation of the markets, the full force of the law should be down upon them, have no doubt about that."

There was a mood of anger and disbelief in the Commons chamber as Tory backbencher Robert Halfon, a long-time campaigner for cheaper fuel prices, said: "This is, if it is proved true, a national scandal and the Government should look at changing the law and put people in prison for fixing oil prices. This has caused misery for millions of motorists up and down the country."

Mr Halfon said despite the Commons unanimously calling for a thorough probe into petrol pricing, the Office of Fair Trading failed to spot any of the allegations currently being probed.

Mr Davey insisted the OFT was "an independent body, it's a strong body, it has powers, it made its investigation. It had a call for evidence, for information, and it is responding to that".

The OFT issued a statement, saying in its earlier investigations "no credible evidence" was submitted to it on the issue of price-fixing but it was now helping the commission in its inquiries.

The SNP's Angus MacNeil called for people to be financially compensated for any wrongdoing. The Western Isles MP asked Mr Davey: "Will the minister ensure if there are any fines, they're passed on to the hard-pressed motorists who might have been ripped off so my island constituents and everybody else's can feel the benefits of any justice?"

Mr Davey pointed out this was the case with the UK regulator Ofgem but not with the commission. "I don't think the law currently allows for any fines levied by the European Commission to be passed on directly to consumers," he said, adding: "What consumers will benefit from, however, would be any lower prices that resulted from freer, fairer markets."