Shares in UK pub firms have plunged after MPs called for the pub industry to be investigated over practices that may be forcing up drinks prices.

MPs want the Competition Commission to investigate arrangements that oblige pub tenants to take beer supplies only from their landlords.

Shares in Punch Taverns and Enterprise Inns were both down more than 17%.

Both firms said they were disappointed with the report from the Business and Enterprise Select Committee.

The committee said the practice, known as the beer tie, led to an "ever-increasing disparity" between pubs and shop prices.

"There... are strong indications that the existence of the tie pushes up prices for consumers," the MPs said.

They added they were "surprised and disappointed" that the Office of Fair Trading (OFT) had been reluctant look again at the beer tie's impact since a 2004 study.