The age-old requirement for corroborating evidence in criminal trials could be abolished as part of changes to the justice system.

The majority required for a guilty verdict would also be increased to two-thirds under the new Criminal Justice (Scotland) Bill.

The Bill, if passed, also raises the maximum sentence for handling knives and offensive weapons from four to five years.

Justice Secretary Kenny MacAskill said: "I have made clear a number of times that I believe that the requirement for corroboration should be abolished as it can represent a barrier to justice.

"It is an outdated rule which can deny victims the opportunity to see those responsible for serious crimes being brought to justice.

"Removing the need for corroboration represents a move towards focusing on the quality of evidence rather than quantity."

But this view is not shared by the Law Society of Scotland which describes corroboration as a "fundamental principle" of the justice system. Removing it will lead to a greater risk of miscarriages of justice, it said.

Raymond McMenamin, from the society's criminal law committee, said: "We believe that removing the requirement for corroborated evidence, without including sufficiently strong safeguards in the Bill, could simply result in a contest between two competing statements on oath and, as a result, bring increased risk of miscarriages of justice.

"The requirement for corroborated evidence is not an antiquated, outmoded legal notion but is a fundamental principle of our justice system.

"It's clear that the concerns expressed by the society and others about juries have been recognised as the Bill proposes a move to a weighted majority from a simple majority, but we don't believe this is sufficient to remove the risks created by abolishing corroboration."

Liberal Democrat MP Sir Menzies Campbell, who practised as an advocate depute for several years in Scotland's High Court, also warned against the changes.

"If the SNP proceed with these proposals, it will confirm that they are not fit to have the stewardship of Scottish criminal law," the former party leader said.

"This is populism at its worst. Corroboration is an essential component of the presumption of innocence and a necessary bulwark against false accusation and injustice.

"As the power of the state increases, the protection of the rights of the citizen has become even more important."

Launching the Bill at a press conference in Edinburgh, Mr MacAskill said: "I have had a few run-ins with the legal profession but I think it's for the right reasons and I think Scotland will be a better place.

"If the price of providing justice for women and children is to ruffle a few feathers in the Faculty of Advocates then so be it.

"Laws are created by the Parliament which is elected by the people of Scotland. As Justice Secretary I am required to weight up the representations from those who practice in the courts of law but I also required to weigh up the interests of those who are affected by the laws of Scotland.

"So I listen the judiciary but I listen to the police. I hear the concerns of the faculty and solicitors but I also note the worries and anxieties of Rape Crisis Scotland, Scottish Women's Aid and Zero Tolerance.

"I believe when you weigh that up, when you consider that (corroboration) appears to come from Romano-canonical law that no other jurisdiction in the Western world possesses then I believe that the interests of justice dictate that we should provide safeguards.

He added: "Equally, we also have to ensure the ability for justice to be done especially for women and children who have suffered in silence often behind closed doors where justice just didn't take place."

The proposal to increase the majority verdict threshold to two-thirds, which would require agreement from 10 out of 15 jurors in most cases, is said to be one of the safeguards to compensate for the removal of corroboration.

The standard of proof would remain proof beyond reasonable doubt.

Any less than two-thirds would be regarded as a "not guilty" verdict. This is to avoid retrials due to hung juries such as the one that reached an impasse at the first trial of former UK minister Chris Huhne for perverting the course of justice.

Scotland's unique "not proven" verdict will be still be available to jurors but it must be reached by a majority.

Mr MacAskill said he recognises the "significant concern" in some quarters about the continuing viability of the not proven verdict, particularly from Labour MSP Michael McMahon who has launched a consultation on its abolition. But he said further deliberation is required.

"I don't think I can pre-judge the work of the Scottish Law Commission. That would be insulting to them and undermine the work that they have to do," said Mr MacAskill.

"We do acknowledge as an administration that there is a bit of a head of steam and certainly significant concern about the not proven verdict. But, equally, there are concerns about doing some major changes at a greater pace and, equally, there are questions about if it were to go, what it would be replaced with."

The Bill would also give police the power to arrest someone on suspicion of committing a crime, replacing a power of arrest that can be used only when enough evidence is gathered. Police will also be able to continue questioning someone after they have been charged.

Detention would be limited to 12 hours rather than the current maximum of 24.

Statements made by the accused to police or investigating officials would no longer be dismissed as hearsay. Courts would also be able to make greater use of television links where appropriate.

Courts would also be given the power to impose greater sentences on those who commit crimes while on early release.

Greater sentences may be also be imposed on public officials involved in people trafficking.