Scotland needs to reverse the "drift towards an unhealthy one-party autocracy," Lord Steel, the former Liberal Party leader, has insisted.

A debate on the constitution in the House of Lords also heard Labour's Lord Wills claim that David Cameron, through his plan for English Votes for English Laws(Evel), had not helped cement the Union but sought to "explode a bomb in Labour territory".

In exchanges, Lord Steel said: "We in Scotland have to wake up to the dangers of the one-party state.

"We are all proud patriots but Nationalism is never of itself a satisfactory creed as has been seen in other countries and can be seen today in the utterances of the cybernats."

The former Holyrood presiding officer said it was to the credit of SNP leader Nicola Sturgeon that she had done her best to "counter" their activities. The First Minister has warned the cybernats, who post abuse online, that they could be disciplined by the party.

"But at the next Scottish Parliament elections, less than a year away, we must roll-back the drift towards an unhealthy one-party autocracy, which we have north of the border," Lord Steel said.

Backing those calling for a constitutional convention, the Lib Dem peer argued that the Lords should be replaced by a smaller senate elected by the component parts of the UK with an "independent element".

Opening the debate, Lord Wills, the former Labour Minister, warned of a "toxic sense of alienation" among voters.

But he said while some of the Government's proposals to tackle this were welcome, others were "partisan and short-sighted" and driven by the narrow political needs of the Tory Party.

Accusing ministers of planning an "onslaught" on the Human Rights Act and attacking plans to introduce Evel, he said the Prime Minister and Chancellor had not tried to build on the Scottish referendum result to cement the union. "Instead," he claimed, "they went out...to explode a bomb in Labour territory."

But Lord Butler of Brockwell, the former Cabinet Secretary, argued that there were UK Government pledges, which needed to be delivered and opposed the call to delay reforms pending a constitutional convention.

The independent crossbench peer acknowledged that the Tory Government was doing much to "fragment power" in the UK but said he welcomed "the direction of march" and many of the planned changes.

"I've never believed the man in Whitehall knows best," declared Lord Butler. "On the contrary, I believe services are best delivered by empowering those nearest to the point of delivery."

Labour peer Lord Lipsey called for his own party to embrace changes to the voting system, noting how under the present first-past-the-post model the chance of Labour gaining an overall majority was "for the foreseeable future, near to nil".

He said the "bias in the electoral system" was against change and that this would be exacerbated if boundary changes went ahead. On top of that, the number of marginal seats had declined and Scotland was now almost a "Labour-free zone".

"I wonder given the Government isn't going to do anything whether my party ought to take the initiative on that; get together with the other parties that have been so badly affected by the electoral system and see if there are any outline proposals."

Lord Bridges for the Government denied the Government's approach was partisan and insisted it was acting in the interests of fairness and one nation.

"There is nothing to suggest the British people want a constitutional convention. The British people want the Government to get on with the job it was elected to do," declared the Cabinet Office Minister.

He added that more powers for Scotland would deliver one of the most powerful devolved parliaments in the world and Evel would help "safeguard the Union".