OTTAWA - New Democrats have produced a series of scathing radio ads lambasting the Liberals for propping up Stephen Harper's minority Conservative government.

The ads come one day after Liberal Leader Michael Ignatieff announced that his party will allow Tuesday's budget to pass, provided that the government agrees to issue periodic progress reports on the budget's implementation and effectiveness.

Ignatieff says his ploy amounts to putting the Harper government on probation but the NDP ads assert that the Liberals are simply rubber stamping the budget.

The ads claim Ignatieff has failed his first test as leader and has thrown in his lot with Harper; they argue that the NDP's Jack Layton is the only leader strong enough to stand up to the prime minister.