Ministers have been urged to make failing takeaways in England and Scotland publicly display their food hygiene scores by a leading backbench MP, after a Guardian investigation found that one in seven had failed their most recent hygiene inspection.

Clive Betts, the chair of the community and local government select committee, said more stringent regulation was necessary to bring the two countries alongside Wales, which insists that restaurants display scores on the premises. Northern Ireland is bringing in a similar requirement shortly.

“There is a real problem at present. The only places that display their scores are the businesses that receive good scores but actually it’s the ones that get a bad score that you need to know about,” said Betts, Labour MP for Sheffield South East.

“I’m certainly very supportive of introducing [a policy of mandatory display],” he said. “What drives businesses is improving their profits and bad scores are going to turn customers away, so there will be a real incentive for businesses to improve their score.”

The ratings criteria are the same across England, Wales and Northern Ireland, and each local authority is responsible for ranking food providers within its boundaries. Food providers are given a score of zero to five. A zero rating signifies that the establishment “urgently requires improvement”, one or two is considered a failing grade, and three to five is satisfactory.

Scotland uses a different system, awarding a grade of “pass and eat safe” to premises that exceed legal requirements of hygiene, “pass” to those that are broadly compliant, or “improvement required”.

In November 2013, it became mandatory for food establishments in Wales to publicly display their ratings, which led to a significant improvement in safety. The proportion of places with a zero rating – the lowest score possible – fell from 0.6% to the current rate of 0.2%.

A similar mandatory display policy will be introduced in Northern Ireland on 7 October. In anticipation of the introduction of the scheme, results in the country have already started to improve. In mid-July, 3% of businesses in Northern Ireland had a failing grade (two or below); by mid-September this had dropped to 2%.

England and Scotland do not require businesses to display their scores on the door or window of the premises, despite having worse overall scores than Wales and Northern Ireland. Ten per cent of establishments in Scotland have been awarded a failing grade (improvement required), compared with 6% in England, 5% in Wales and 2% in Northern Ireland.

Betts called the food inspection service “one of the unsung services of local government” – a service the public doesn’t usually notice, but would “suddenly become aware [of] if they weren’t there”.

“There is a worry with cuts to local authorities and budgets, food inspection is one of the areas that has been hit the hardest, so it’s important that what work they do do gets results,” he said.

Cuts to local government funding have meant the number of food inspectors has declined in recent years. The ratio of food safety inspectors to businesses has dropped from 4.2 full-time inspectors per 1,000 food businesses in 2012-13, to 3.7 per 1,000 in 2014-15. This figure is dragged down considerably by England, where there are only 3.2 officers per 1,000 businesses, compared with 5.7 per 1,000 in Scotland, Wales and Northern Ireland.

Betts said that as well as being effective, a mandatory display scheme was likely to be cost-effective.

“The inspections are done, so there’s no extra cost to the local authority and there’s no cost to the business of sticking something in the window,” he said.