Shadow home secretary David Davis restated the Conservatives Party's plan to scrap the government's ID card scheme in a speech to the party's conference in Blackpool yesterday.

"We'll scrap ID cards, that expensive white elephant. Put some of the early savings into extra prison places," he told the party faithful.

In February, Davis wrote to ministers and companies expected to bid for the plan, warning that his party would axe the project if it came to power, in an unprecedented move that sparked anger from suppliers. Trade body Intellect said the Tories announcement would cast doubt over the future of other public procurement plans.

But Davis's conference speech comes as the main parties gear up in anticipation of a possible general election in November, adding extra spice to the Conservatives' threat.

The party also launched an electronic petition as part of its 'Bad IDea' campaign, arguing that ID cards would not prevent terrorist attacks or identity fraud, in an indication that ID cards are seen as a likely election battleground.

It also attacked the cost of the plan, rubbishing government estimates that it would cost £5.4bn and instead citing figures from the London School of Economics that suggest the price tag could reach £20bn.

A campaign statement aimed at voters says: "According to Government estimates, you will pay at least £93 for a combined ID card and passport package but, given this government's appalling record of implementing IT projects, this figure is likely to go up."

The party also warned that the ID cards "could hold almost 30 separate pieces of personal information" on individuals.