A Coalition federal government would impose tougher measures on foreign investments based on plans outlined in the discussion paper unleashed by Opposition Leader Tony Abbott on Friday.

Under the watch of Mr Abbott, should he become prime minister, the Foreign Investment Review Board (FIRB) would automatically look into foreign takeover of local agricultural businesses worth beyond the $53 million mark.

The new regulatory firewall planned by the Liberal-National alliance would also necessitate the FIRB's prior nod on land purchases by foreign entities that are valued $15 million and up, possibly pushing down the current minimum cap of $244 million.

The whole plan, according to Mr Abbott, was designed not to turn away foreign investments but to finetune their influx in manners that exclusively serve Australia's best interest.

"I want to make it absolutely crystal clear that the Coalition unambiguously supports foreign investment in Australia," the Liberal leader was reported by ABC as saying on Friday.

The proposal, he added, places well-deserved premium on the notion that "the public have confidence that the foreign investment we need and want is in Australia's national interest."

What the plan intends to achieve, according to Shadow Treasurer Joe Hockey, is to provide openness in crucial business transactions, stressing that "if we have greater transparency, without a massive increase in red tape; if we have greater scrutiny, it will reassure Australians about the value of foreign investment."

Mr Hockey told The Australian on Friday that the Coalition was not planning to scare away foreign investors as he admitted that with the present insufficient levels of national savings, cash coming from abroad would be required to finance further business developments in the future.

However, the ideas contained in the paper drew flak from former Liberal minister Peter Reith, who labelled the plan as bordering on populism and contrary to public interest, as claimed by Mr Abbott.

In an interview with The Australian, Mr Reith, who served under the Howard Government, described the foreign investment tweaks as "wrong in principle ... and just a quick fix to satisfy the (Nationals), but which will come back to bite the national interest."

"The fact is you put some agri-pollie with ambitions onto the FIRB, they'll be out there pushing the issue along on a regular basis, basically funded by the government. It's just crazy, stupid politics," Mr Reith warned.

He strongly suggested for Mr Abbott to submit the plan before the whole Liberal roll and urged on backbenchers to voice out their take on the matter.

In a reaction, Federal Treasurer Wayne Swan called the Coalition proposal as a 'dog's breakfast that even some in Liberal could not swallow.

"We've got a range of possibilities canvassed in this paper that just send very confusing messages about what the Liberal party stands for," Mr Swan was quoted by the Australian Associated Press (AAP) on Friday.

In contrast, he added, "the Government has a very strong set of national interest guidelines which govern state-owned enterprise investment in Australia."

Also, Finance Minister Penny Wong took the Coalition discussion paper as a clear signal of its intent to erect government barriers that could hurt the steady flow of foreign investments to Australia.

"I think you'd certainly be seeing a lot more regulatory hurdles to foreign investment ... and it is a pretty big burden of red tape to be starting to say we're going to scrutinise everything," Mr Wong told Sky News on Friday.

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