Three lawmakers joined the snowballing opposition on the controversial $8.4 billion buyout proposal of the Australian Securities Exchange (ASX) by the Singapore Exchange, further establishing hurdles that need to be dealt with by the stock exchange merger.

Independent Tasmanian MP Andrew Wilkie, Australians Green MP Adam Bandt and Western Australian MP Tony Crook all declared on early Thursday that they would oppose the planned sale of ASX.

They jumped on the apparently growing bandwagon that balked at the idea of ceding the nation's prime stock exchange market to a foreign entity, which first must gain the approval of Australian regulatory agencies and the green light of the federal parliament prior to its realisation.

The ASX-SGX merger could lead to the creation of the world's fifth largest share market but Mr Bandt appeared far from impressed as he observed that giving up control of the country's stock market to SGX, which is 25 percent owned by the Singaporean government, would be detrimental to Australia's national interest.

Going ahead with the sale, he maintained, would be a big mistake especially to a country like Singapore, which he described as a state with no functioning democracy, as he stressed that the ASX is fundamentally Australian and must stay as it is.

On his part, Mr Wilkie cited the local economy and the nation's sovereignty as the prime reasons for his reservations as he challenged the federal government to prove the merits of an ASX takeover by a foreign company though he quickly added that "I would not support any move to sell the ASX to interests in Singapore."

On the other hand, independent MP Rob Oakeshott seemed more open to the prospect of an ASX being controlled by Singapore so long as the Australian Foreign Investment Review Board (FIRB) would give the proposed merger sterling recommendations.

Mr Oakeshott noted that the city-state is one of Australia's solid trade partners, which he emphasised provides for a vaunted reason "to develop links and strengthen our financial centre."