Lord Falconer, the lord chancellor, will today face accusations of introducing American style economy justice to Britain by planning to save millions of pounds through putting out all criminal legal aid aid in London to the lowest bidder.

The announcement, to be made at a press briefing by the legal aid Services Commission, is part of a pounds 292m cuts package offered by Lord Falconer to the pounds 21bn Whitehall savings programme launched by Gordon Brown. All the major law associations - from the Criminal Bar Association to the Solicitors Association of Higher Courts Advocates - are united against the lord chancellor's decision, which may lead to some practices boycotting the scheme. It will be implemented on July 1.

Lord Falconer has targeted the legal aid aid budget as a main area for savings rather than imposing big job cuts or negotiating better deals for goods or services.

A paper on the Department for Constitutional Affairs website reveals that the ministry plans to make pounds 173m cuts from the legal aid aid budget, growing at up to 8% a year.

The ministry wants to freeze spending while funding more court cases.

London has been chosen to test what the legal aid Services Commission calls "price competitive tendering" because it is responsible for 20% of the pounds 2bn a year legal aid aid budget - the largest proportion of any region in Britain.

The paper says the changes should be seen as "part of a wider series of reforms to help control both civil and criminal legal aid aid expenditure.

"This has seen us move from a system of paying for legal aid aid work at hourly rates set by the courts, to systems based on prescribed hourly rates and standard, graduated and fixed fees."

In an advice note, the government admit that the new system will lead to fewer firms bidding for the work with less choice for clients.

Lawyers are expected to express strong criticisms of the new proposals.