Ahead of a major speech for the cross-party Better Together campaign, the former home secretary insisted it was not unpatriotic to vote against independence.
He also argued Alex Salmond's refusal to accept independence carried risks was undermining the Yes campaign.
Baron Reid of Cardowan, who served in nine Cabinet posts under Tony Blair, is due to address an audience in Stirling today as both sides in the referendum fight step up their campaigning.
The campaign enters its final 100 days on Monday and both Better Together and pro-independence rivals Yes Scotland are planning official launch events.
The Scottish Government will mark the day with an event in Edinburgh for women's organisations, hosted by Nicola Sturgeon and other female cabinet ministers.
Lord Reid urged voters to consider the advantages of being in the UK and the risks of leaving, which he said included a threat to pensions and uncertainty over the currency.
But he added: "The third issue is about national consciousness and its one of the heart more than the head. Most people feel very Scottish and proud of it but they are also proud of being part of the UK and British. Many also feel a little bit Irish or Lithuanian or Pakistani, or Polish or whatever. What's important is that no side in this argument has a monopoly on patriotism.
"A No vote does not make you less Scottish. A No vote is not a vote against Scotland it's a vote to protect Scotland, Scotland's interests and the welfare of the people of Scotland and that has to be made absolutely plain."
He added: "I firmly believe that, it would be helpful if the First Minister was also able to publicly recognise that because he is First Minister of Scotland and not just a particular group of people."
Lord Reid said people were becoming "increasingly sceptical" about independence being risk-free.
He said: "I think there is a growing worry that, however committed he may be, the First Minister is becoming blinded by his political ambitions and political objectives to the realities and risks of separation.
"I think that's what's moving people back to a position of believing the advantages of being in the UK outweigh the risks of separating."
He also hit out at the increasingly abusive tone of the debate, especially on Twitter and other social media.
"It's unfortunate, it's disappointing, it's not something the vast majority of people want to see defining or even influencing a campaign," he said.
"I accept the sincerity of those who disagree with my point of view.
"I don't question their love of this country or their patriotism. I would hope they would do likewise with those who disagree with them.
"The key thing is to conduct the debate in a way that does not avoid the hard questions but avoids some of the abuse we have seen principally but not exclusively from so-called cybernats and others."
Lord Reid entered the campaign as Better Together prepared for an intensive week of campaigning. Alistair Darling will speak in Glasgow, Edinburgh, Stornoway and Inverness on Monday and Tuesday.
Labour's Jim Murphy and Gordon Brown, LibDems Shirley Williams and Charles Kennedy, and Tory MSP Annabel Goldie will take part in events across the country.
Mr Darling said: "We are now at the business end of what has already been a long campaign."
Yes Scotland will unveil plans tomorrow for a major programme of events during the final 100 days of the campaign.