Interim Liberal Leader Bob Rae and NDP Leader Tom Mulcair traded shots with each other Wednesday over how their respective parties are responding to the Conservative budget.

They each voiced their opposition to Prime Minister Stephen Harper's latest budget plan, tabled last Thursday, but Rae and Mulcair were also taking aim at each other.

Rae began the day by delivering a public speech to his caucus during which he outlined what is wrong with the Conservative budget and he promised that his party will undo the damage that will be done to Canadians by the plan.

Rae said the budget fails on all fronts – it doesn't improve Canada's prosperity, the country's environmental sustainability, the strength of Canada's federation or its role in the world.

He took particular aim at the government's intention to raise the eligibility age for Old Age Security from 65 to 67.

"The determination by this government to raise the age of retirement for the most vulnerable from the age of 65 to the age of 67 is a breach of every single promise Stephen Harper has ever made," Rae said during a lengthy speech.

"The only good news we have is to say clearly and categorically the Liberal party will undo that damage. We believe that the age of retirement should still be 65," he said.

Rae told his party they have to get Canadians to appreciate what is at stake in this battle against the government over the budget, which he described as "a direct assault on income security on the most vulnerable citizens in our country."

The Liberal leader said his party would "restore each and every one of the cuts" to foreign aid.

In addition to laying out his criticisms of the budget, Rae also spent a portion of the speech on the auditor general's findings on the F-35 fighter jet program, released Tuesday.

He said while Prime Minister Stephen Harper and the Conservatives like to lecture others on sound fiscal management, their handling of the F-35s is "the worst example of economic incompetence and of fiscal dishonesty that this country has seen in a generation."

Rae calls Mulcair a 'mini-Harper'

Rae made a point during his speech of saying that he would have liked to respond to the budget earlier in the House of Commons but that the NDP prevented other MPs from speaking on it.

He blamed the newly elected NDP leader for the tactic used by his party's finance critic, Peter Julian, that saw him talk for more than 13 hours on the budget.

As the first Opposition MP speaker, he had unlimited time, and he managed to keep talking – thereby preventing the Liberals from having their turn to respond.

Julian filled the time by reading messages from Facebook and Twitter, provoking much frustration among the Liberals, but New Democrats say it's legitimate for them to use their time as they see fit and that they were expressing the concerns of Canadians.

The Liberals don't see it that way. Rae said he phoned Mulcair and offered his congratulations after he was elected on March 24 and that his response apparently was a deliberate attempt to prevent the Liberals from having their turn in the House.

"As a strategy or even a tactic it was clearly a failure. If there was any doubt in anyone's mind in Canada, let me just say that the era of love and good feeling is clearly over inside the NDP. It's a new regime," he said in his speech.

"We've now moved to the world where anger apparently is better than love, arrogance is now better than humility and petulance is much stronger than respect," he said, invoking the language used in the letter that the NDP's late leader Jack Layton wrote to Canadians before he died in August.

Rae suggested that Mulcair is acting like a "mini-Harper" and that the delay tactic "says a lot about the new NDP."

Mulcair says Rae having a 'tough week'

Julian finally wrapped up his speech late Tuesday afternoon and Liberal MPs had about 20 minutes to talk about the budget and to propose their own subamendment before the time allotted for the day was done.

There is a motion before the House that the budgetary policy of the government should be approved in general and the NDP's amendment to it said the budget should be rejected for various reasons including that it will increase unemployment and cut services.

The Liberals' subamendment proposed that Harper shouldn't be allowed to collect the retirement bonus he is entitled to until he is 67. They claim it is a double-standard that he would be eligible for the benefit at 65 while Canadians will have to wait longer for OAS cheques.

Both the amendment and the subamendment failed when they were put to a vote Wednesday.

On Wednesday night, there is a vote on the government motion in support of the budget.

Mulcair responded to Rae's blunt criticism by saying the Liberals only used 11 minutes of their time and that shows "they don't have anything to say about the Conservative budget because like usual they actually agree with the Conservative budget."

He said Canadians are relieved that the NDP is the Official Opposition, a party that he said will stand up to Harper as opposed to when the Liberals were the second party.

Mulcair also criticized the budget and the cuts to public services he said will stem from it.

"They promised us a program of job creation instead we have 19,000 job cuts in the civil service," he said.

Mulcair also took a dig at Rae and suggested that he feels threatened by Liberal MP Justin Trudeau and the attention he has received recently because of his charity boxing match last Saturday with Conservative Senator Patrick Brazeau.

"There's something else that's obviously in the wind as well. I believe that Mr. Rae is quite concerned about the arrival of Mr. Trudeau on the scene and the recent attention being paid to him, so I think he's having a bit of a tough week," he said.

Rae, in turn, later told reporters that it's not true that Liberals only used 11 minutes and that, "Mr. Mulcair would not know the truth if he ran into it in broad daylight."

He said the delay tactic was an "ego trip" by the NDP, and that he's "not impressed" that Mulcair would say his party sides with the government.