Councillor Mike Cooper, who led the party until July 2019, said: “I think it’s going to cost us a lot of money in the long run.”
Last Thursday, he voted against the alliance, which will see both authorities share senior officers and look to save £15.4m through further joining of the workforces over the next 10 years.
“There was a lot of interference into those decisions that were made. The MP got involved and interfered and things, and stuff like that and it was really wrong what was done,” said Councillor Cooper.
Councillor Cooper has previously left the party for a short stint as unaligned, but rejoined in the week that another former Boston leader, Councillor Aaron Spencer, resigned in January 2020.
Councillor Spencer, who has sat as unaligned since he left the party, has since only attended three of the nine meetings he was expected to be present at across both his Lincolnshire County Council and Boston Borough Council seats.
He was absent from last Thursday’s meeting which saw the alliance approved by just one vote, but had voted in favour of a delay at the previous one.
Councillor Cooper said his impressions of the party after leaving twice were that it “handles things pretty badly actually.”
“The way things have gone the last 12 months, it’s not very good.
“They’re in a bad place as an organisation, certainly within the Boston area, and they need to get their act together.”
The latest move means the Conservative grouping on Boston Borough Council sits at 15 out of 30 councillors – with one of those being Independently-elected but Conservative-aligned Councillor Tracey Abbott.
Boston Borough Council’s current leader Councillor Paul Skinner said Councillor Cooper’s move sounded “like status quo” for the party.
“All I can say is that for a time he hasn’t been a party member anyway. He’s just been associated with the group, and at the end of the day, we’re all free to make choices in life, even if they’re flawed,” he said.
“I’ve just found it a bit disappointing, but I did expect it to happen because of the way he voted in the last two council meetings.
“We don’t have a whip, despite rumours. We have consensus of what we do and we expect people to support it.
“Quite frankly, maybe he doesn’t want to face the group – that could be it.”
He said allegations the alliance would cost too much were “absolute rubbish” and called Councillor Cooper’s other allegations “outlandish”.
He said what was in the paperwork “is deliverable”.
Earlier this week opposition councillors announced they were launching a judicial review due to a lack of scrutiny and information.
However, Councillor Skinner said the allegations were “absolute silliness” adding: “All the details to make up your mind are included in the papers.”
He said he had run several briefing groups ahead of the meeting to give information.
“The strength of togetherness is well worth it,” he said, adding that the cost savings would be “ploughed in to services to maintaining and enhance them”.
He moved to reassure taxpayers that the council would not be paying the costs of the review.