Federal Opposition Leader Brendan Nelson has denied he plans to block the budget legislation in the Senate.

"We'll do no such thing," he told Fairfax Radio Network this morning.

• Cut petrol excise by 5 cents a litre
• Block Labor's proposed alcopop tax increase
• Block increase to Medicare surcharge income threshold
• Lower capital gains exemption to 5 years for small businesses
• Lift entry requirements for teacher training
• Increase carers benefits

"Of course, we're not going to block the budget.

"It would be completely irresponsible to do so.

"But we certainly are looking at some of the tax measures."

The opposition has the ability to block legislation in the Senate, where it still has a majority until July 1.

Dr Nelson said the opposition would vote against the increase in tax on ready-mixed drinks, also known as alcopops, because it would do nothing to curb binge drinking by young people.

"The government itself is saying that consumption will continue to increase very significantly and those who don't buy these things will go on to other forms of alcohol or perhaps even a drug."

Rather than target the price of one alcohol product, the opposition would assemble a group of experts to consider the whole problem of alcohol abuse.

"What I'm intending to do is to bring together specialists who work in this field - a health economist, parents, police and a variety of people who have an interest in and expertise in this field, to develop a comprehensive approach which might actually assist us dealing with alcohol abuse and ... binge drinking by young people."

Asked why he was proposing a cut in petrol excise, when the coalition had opposed this for the past 11 years, Dr Nelson said it was the one thing a government could do to reduce the price of petrol.

"I've been on a listening tour and the single most important thing for Australians ... is the cost of petrol," he said.

"Watching petrol prices will not bring them down. The one decisive thing that a government can do is reduce the tax on petrol."

It would be a modest measure, but it would help families, he said.

"I don't think that perhaps since 2001 has the cost of petrol been the concern and stress on Australians that it is today."

The opposition also would be taking a very close look at the increase in tax on luxury cars, Dr Nelson said.

"There are a number of issues. If you increase the tax on so-called luxury cars you actually increase the price of cars below that threshold, that's the first thing I want to have a look at."

The second thing was that families with a large number of children needed a larger car or people mover, such as a Toyota Tarago, whose cost might exceed the threshold.

"The thing we're concerned about is, the government didn't say there would be any tax increases before the election, now we've got $19 billion worth of tax and revenue measures over the next five years.

"What we are concerned about is that there's $15 billion in cuts to expenditure, there's a $30 billion increase in expenditure and $19 billion in taxes being applied to people, one of which is this Tarago tax (on vehicles priced at more that $57,000)."

The budget changes to the Medicare surcharge threshold would lead to an increase in premiums for private health insurance, Dr Nelson said.

"The net result is $300 million less a year going into hospitals, fewer people in private insurance ... and that means higher premiums paid by the people left in it, predominantly pensioners, retirees and families."

The coalition would oppose the Medicare changes as well as the changes to taxes on luxury cars and ready-mixed drinks, he said.

"No Australian was told there'd be increases in taxes," he said.