It is understood that Labour intended to include five promises on the card, as it had at the 1997 and 2001 elections, but that immigration was added at a late stage in an attempt to combat a Tory offensive.
In a back-handed compliment to Michael Howard, Labour will promise "strict conditions that work" for asylum-seekers. The move is a recognition that the Tories have forced Labour on to the defensive by announcing a hardline policy including an annual immigration limit and quota of asylum-seekers.
"Controlled immigration" is one of the Tories' five pledges - along with school discipline, more police, cleaner hospitals and lower taxes.
Labour's six promises will cover similar ground, although they will leave the sensitive question of tax policy to the party's manifesto. Labour's economic pledge highlights stability, the national minimum wage and help for first-time home buyers.
According to today's New Statesman magazine, the other pledges are a commitment to cut NHS waiting times; discipline in schools; "effective local policing"; and more nursery provision, maternity and paternity pay, and greater emphasis on the work-life balance.
Mr Blair will step up the "pre-campaign" in a tour of marginal seats today en route to the party's spring conference in Gateshead. He will launch the economic pledge with Gordon Brown at a signing ceremony in London. This will be the first pledge on the card to highlight its importance at the election.
The Prime Minister hopes the pledges will help restore faith in him and his Government after his trust ratings fell following the failure to find weapons of mass destruction in Iraq. He will insist that Labour has honoured its 1997 and 2001 promises.
A Labour spokesman said last night: "We have delivered on the fundamentals. But elections are about the future, not just our record or our opponents' record. We intend to fight a positive, upbeat campaign, focused on our promises for the future."
After being criticised for attacking Mr Howard's record as a minister, Labour is determined to make the economy and public services the bedrock of its campaign. Its polling shows it is well ahead on these issues.
Other ministers involved in today's launch will be John Prescott, the Deputy Prime Minister, Charles Clarke, the Home Secretary, and Ruth Kelly, the Education Secretary.Reuse content