The government is under pressure to increase the value of vouchers in the Healthy Start scheme, which provides low-income families with free milk, fruit and veg and infant formula.

Trade body Dairy UK has complained to the Department of Health that the value of the vouchers was fixed at £2.80 in February 2004 - two years and nine months before the scheme was finally rolled out.

It says the figure should now be raised to at least £3.10 to keep pace with inflation - a view supported by the Fresh Produce Consortium. "We urge the government to provide the half a million qualifying needy mums and families with this benefit at today's real levels - not a figure first suggested as a minimum nearly three years ago," said Dairy UK company secretary Simon Bates.

A Department of Health spokesman said: "The vouchers are intended to provide a reasonable financial contribution to the costs of a healthy diet for qualifying pregnant women, babies and children but are not intended to fully provide for those costs."

Voucher values would be reviewed annually in the light of any milk, fruit and veg price rises, he said. "It's too early to review voucher values at this stage. We will review them for April 2008."