More than £400,000 was spent by the Welsh Assembly Government on external public relations firms in a year.
A Freedom of Information request shows it used external PR firms from April 2009 to March 2010.
Conservatives said it spent vast sums "blowing its own trumpet" and Liberal Democrats said it had to cut costs.
The assembly government employs 25 full-time PR and communications staff, but it said PR firms' role was "very different" to that of the press office.
The assembly government used external public relations companies to 31 March this year, at a cost of £400,123.
The response to the FoI request said the external firms were used to "support communications to the Welsh public on a wide variety of government policies, including campaigns on issues such as anti-bullying".
Peter Black, the Welsh Lib Dems' finance spokesman, said: "With 25 in-house press officers and public relations staff, you'd hope that the Labour-Plaid government wouldn't have to pay large amounts of money to external consultants.
"We've been warning this government for a while that they have to cut back on the amount of money they spend on external consultants and rely on in-house experience to save money."
Conservative finance spokesman Nick Ramsay said families cutting their budgets would be "disappointed to see the assembly government spending such vast sums blowing its own trumpet".
He added: "I am confused as to why ministers are spending so much on external PR companies when they employ their own staff to deal with such matters.
"The assembly government, like all public bodies, has to duty to spend money wisely and must crack down on any frivolous and wasteful spending."
The assembly government said its press office offered a seven-day-a-week service across all ministerial portfolios dealing with press queries, writing articles and managing the assembly government's online news service.
A spokesperson said: "External PR companies are sometimes used as part of the [assembly] government's wider policy activity.
"Their work will usually involve intensive specialist projects over and above press office activity.
"Examples of campaigns supported by PR companies include the Climate Change Champions and skillscymru - the largest careers and skills event ever held in Wales.
"Work is commissioned on a case-by-case basis and carefully evaluated to ensure value for money."