David Cameron was accused of stoking up a national fuel crisis after urging motorists to "top up" their tanks despite the fact no strike by tanker drivers has yet been called.

Labour branded the UK Government's advice irresponsible and insisted that, instead of raising fears of a fuel shortage, it should be sending a message of "business as usual" given unions have, by law, to give at least seven days' notice of industrial action.

As queues formed at petrol stations in the first signs of panic buying following the Prime Minister's advice, some forecourts reported they had already run dry.

Petrol sales are up 45%, while diesel sales have risen 20% compared with normal.

Shadow Treasury Minister Chris Leslie branded the Government "incredibly irresponsible" after Cabinet Office minister Francis Maude urged people to stockpile fuel in jerry cans.

He said: "I heard Francis Maude was telling people to start filling jerry cans, panicking people all around the country, which is an incredibly irresponsible action to take.

"If you stoke up the rhetoric and you end up fuelling the flames, as the Government seem unfortunately happy to do, that is a very irresponsible thing."

Mr Leslie also suggested motorists were being used in a "political game", to divert attention from the Government's problems over the Budget and the cash for access row.

Garages from Edinburgh to Aberdeen reported a busy trading day, but appealed to drivers not to panic.

Staff at Sainsbury's petrol station in Woodlands Road, Glasgow, revealed its head office had already delivered posters to stick on pumps in case they ran out of fuel.

In Aberdeen, more than 40 cars queued to fill up at one supermarket, with dozens of motorists causing tailbacks while trying to get to the forecourts of Sainsbury's Bridge of Dee branch.

At Morrisons in Inverness, staff reported an upsurge in petrol sales.

One employee told The Herald: "I wouldn't have thought it would affect us up here, but there have definitely been more customers coming through today, mostly putting in £40 worth or taking half a tank.

"We will definitely have enough petrol, though, to keep going."

Perth-based Stagecoach, which operates 8100 buses in Britain, said it was well-prepared, given a £1 million investment in expanding its fuel stores.

"We have been monitoring the situation and have been liaising with Government and our fuel suppliers to ensure we have robust contingency arrangements in place," said a company spokeswoman.

Mr Cameron yesterday sought to calm fears of a potential fuel shortage, which Downing Street had raised earlier this week, stressing there was "no imminent strike". He added there was "no need to queue" for petrol and made clear there was "absolutely no justification" for industrial action.

The Prime Minister, who chaired a meeting of the civil contingencies committee, Cobra, added: "If there is an opportunity to top up your tank, if a strike is potentially on the way, then it is a sensible thing if you are able to do that."

The Retail Motor Industry Federation said the "Government appears intent on creating a crisis out of a serious concern".

Earlier, Mr Maude was criticised by the Fire Brigades Union for suggesting drivers should stockpile petrol.

The dispute involves tanker drivers' at five of seven haulage companies and centres on terms and conditions as well as safety standards. If it goes ahead, it threatens disruption for millions of motorists and their families over the busy Easter Bank Holiday weekend next week.

Acas, the arbitration service, was still seeking to organise talks between union leaders and haulage representatives.

Last night, a Scottish Government spokesman said both sides should negotiate.

He added: "This is a trade dispute between the tanker drivers and their employers, and Scottish ministers are closely monitoring the situation, and have been in touch with the industry and UK ministers. The Scottish Government and its agencies meet on a regular basis, to plan and prepare for potential situations.

"We continue to be in regular contact with industry and agency partners to assess any developments and progress contingency plans."

Downing Street said Cobra had discussed a range of plans, aimed at getting supplies to emergency and essential services and to build up a "level of resilience" in the system for businesses and motorists.

Around 80 RAF drivers are already being trained to drive commercial tankers and this number could increase to 200.

Mr Maude accused Unite and its leader Len McCluskey of being "irresponsible" as well as warning that "lives were at risk" if strikes went ahead.

Labour leader Ed Miliband said: "We know we can't afford a strike. The way that is avoided is by proper negotiation."

l A strike at Mahle engineering in Kilmarnock, planned for today, has been suspended after the company presented fresh proposals over the plant's future. A 28-day extension has been agreed to allow the workforce to discuss the latest move.