The Government has insisted plans to give traffic wardens new powers to impose fines of up to £100 on motorists were not a money-making exercise, but were designed to keep traffic moving.

Transport Secretary Alistair Darling said the measures, which allow local authority parking attendants to punish minor motoring offences, would help police concentrate on more serious matters.

"Police have got better things to be doing," he said. "When you invest all that money training a police officer, I think most people would like to see them dealing with other criminal matters that are of more pressing need."

Mr Darling added that work such as patrolling bus lanes could be done by traffic wardens as long as they were properly trained.

But he said they must not overstep the mark to the extent that people felt they were being "put upon".

The measures set out in the Traffic Management Bill were being debated by MPs as Parliament returned after the Christmas break.

The Bill is expected to give local councils new powers to fine not only utility companies whose roadworks disrupt traffic, but also motorists who block other drivers by wrongly entering yellow box junctions or turning right across a restricted lane.

Tories vowed to oppose the proposals, which transport spokesman Damian Green denounced as "thinly disguised ways of extracting even more money from the already heavily-taxed motorist".

Under the terms of the Bill, which received its second reading on Monday, drivers who violate "no right turn" rules or block junctions will have their number plates automatically photographed by traffic cameras.

But with growing controversy over the widespread use of speed cameras and the imposition of fines, offenders are unlikely to be further punished by having penalty points added to their driving licences.

The jam-busting Bill, unveiled in the Queen's Speech in November, also introduces fines of up to £5,000 for private companies which allow roadworks to overrun, causing misery to motorists caught up in tailbacks.

And it includes provisions for uniformed Highways Agency officers to patrol motorways to get traffic moving after road incidents or breakdowns.

Mr Green said the measures were no substitute for the road-building programme cancelled by the Government soon after Labour came to power in 1997.

"We desperately need to tackle congestion on our roads, not least because in 1997 the Government scrapped more than 100 schemes which would have helped alleviate the problem," he said.

"This Bill is not the answer. It is a series of half-baked schemes, some of which are thinly disguised ways of extracting even more money from the already heavily-taxed motorist.

"The Conservative Party is opposing the second reading of the Traffic Management Bill as a huge wasted opportunity.

"The new powers for local authorities to fine drivers for a wide range of offences is likely to extend the anger already felt by millions of motorists over speed camera fines.

"The new special motorway traffic wardens will have both the duty and the power to tow broken-down vehicles away and this may well interfere with the excellent work of the AA, RAC and other breakdown services, leaving motorists paying twice.