The Assembly Government's budget could be cut by almost £300 million as a result of Gordon Brown's £5 billion planned efficiency savings, Welsh Conservatives have learned.
Information obtained by Shadow Health Minister Jonathan Morgan AM suggests a cut of up to £292 million is to be introduced in 2010-11 following last week's pre-Budget report.
The Cardiff North AM warned that slashing hundreds of millions of pounds from the Assembly Government's budget could have grave consequences for public services in Wales.
Mr Morgan said Labour-Plaid ministers must reassure public sector workers about how it intends to plan for the proposed spending downturn.
Welsh Conservatives will not sit back and allow teachers, doctors and nurses to lose their jobs, he added.
Shadow Health Minister Jonathan Morgan AM said: "People should be under no illusions - Gordon Brown's so-called efficiency savings could mean cuts to frontline public services in Wales.
"The fact we are set to lose almost £300 million will come as a huge shock to the people of Wales whose public services rely on this money.
"It is also a concern to all those working in the public sector, including teachers, doctors and nurses, who will now be wondering what this cut means to them.
"We will be seeking assurances from the Assembly Government as to how this cut will be accommodated in its spending plans.
"As a party Welsh Conservatives will not sit back and allow teachers, doctors and nurses lose their jobs.
"Cutting up to £292 million in the Assembly's budget will have serious, long-lasting implications for services across Wales that everyone relies on."
Shadow Secretary of State for Wales Cheryl Gillan MP said: "Ministers need to be open and honest with people. They had the chance to come clean last week about how its efficiency savings will affect Wales. They failed to do so."