Douglas Ross also said he hoped Labour and the Liberal Democrats would reconsider the idea of forming a coalition against the SNP in Holyrood.
In a speech given to think tank Onward, Mr Ross also put forward a range of ideas to strengthen the power of Holyrood and MSPs to prevent any Scottish Government abusing power again.
He argued for reforms to split up the dual role of the Lord Advocate and to prevent the First Minister from being in sole charge of ministerial code investigations.
Further proposals include a Holyrood equivalent of elected select committee chairs and a right to recall for disgraced MSPs in exceptional circumstances.
He also called for enhanced parliamentary privilege to prevent the situation where the Crown Office stopped MSPs from considering Alex Salmond inquiry evidence that had no risk of identifying a complainer.
Mr Ross said: “It is time to shatter the comfortable illusion that Scottish democracy is superior and accept that it can and should be improved, that we look at practice elsewhere – and that includes even at Westminster – for inspiration.
"[It’s important] that we reassess after more than 20 years the effectiveness of the Scottish Parliament and empower it with the tools that it needs to properly scrutinise government.
“This should be a cross-party commission, I do not pretend that the Scottish Conservatives have all of the answers.”
Mr Ross pointed to a report by the London School of Economics, which he said highlighted some of the potential difficulties for Scottish economy.
He said: “What the process would be if we had an independent Scotland negotiating leaving the United Kingdom – well, it would be immensely worse than the difficulties that were experienced in leaving the European Union.
"We would be leaving a country that we remain part of, that we have been the proud and strong member of for centuries, rather than for the European Union for just over four decades.”
In response to a question from the floor as to whether the Scottish Tories would consider “some kind of grand coalition in order to preserve the union and potentially prevent the SNP from from gaining power”, Mr Ross said he would.
He said: “Yes, because I believe that the last 14 years of failure that we've seen from the SNP has undermined everything we're trying to do in Scotland. Surely we can work together and put aside our political differences to work together, especially on our recovery from coronavirus over the next five years, rather than more fights over the constitution, and we can only do that by stopping an SNP majority.
"If we can also work together as political parties, I would be quite happy to do that – and indeed I made that offer to the former Scottish Labour leader and he dismissed it.
"I then made that offer to the two candidates who were seeking the leadership of the Scottish Labour Party, Anas Sarwar and Monica Lennon, and they turned that down within 30 minutes. But I hope they reconsider.”