A Somerset MP has accused the county council of spending "ultimately about £20M" on a new IT system – just 12 months before it formally ceases to exist.

Ian Liddell-Grainger, the Conservative MP for Bridgwater and West Somerset, used parliamentary privilege to claim there was "no urgent need" for Somerset County Council's new IT investment.

The council has responded that the new system is essential for running payroll at the new unitary authority, which will formally take control on April 1, 2023.

Officers added that making the changes would save taxpayers more than £5.5M upfront and lead to lower running costs, meaning more money could be provided for front-line services. Mr Liddell-Grainger – who has represented his current seat since 2010 – made his statement in the House of Commons on March 17 using parliamentary privilege (meaning MPs cannot be sued for anything said in the House). He said: "Somerset County Council is about to spend £8M on a computer system that will ultimately cost about £20M. IT projects in this country have a pretty shabby history.

"The problem we have is that there will be unitary elections in May, with the four district councils still there, but the system will be neither one thing nor the other.

"With counties and districts buying expensive systems that inevitably tend not to work, may we have a debate in this House on IT projects?" Mark Spencer MP, the leader of the House of Commons, responded: "My honourable friend is a tenacious campaigner on local government reform, and this is not the first time he has mentioned Somerset councils in the chamber.

"I know he will continue with enthusiasm to hold them to account and ensure they deliver for his constituents."

Following his statement in the Commons, Mr Liddell-Grainger clarified that the £20M figure was entirely his own prediction, and stressed his comments were not an attack on the current Conservative administration (with which he has had many public disagreements).

He told the Local Democracy Reporting Service: "The county council is minded to order a new IT system to serve the new unitary, including four district councils who each have their own complex IT systems.

"The current cabinet want to use MS Dynamics. But the work to see if the MS system can be tailored properly for all IT needs has only recently begun.

"The cabinet believes it will cost almost £8M. The truth is it will probably cost an awful lot more to integrate every need satisfactorily – if such integration is possible at all. I reckon £20M is the likely bill.

"My concern is two-fold and non-political. For a fag-end cabinet to order a system to be used by a totally new council just seems wrong, unless there is an urgent need to replace everything now. There is no such urgent need.

"The decision could be safely taken later when a new administration is in charge. That is the only honest and fair way to proceed.

"I am also acutely conscious of the fact that the council has a very tarnished track record in ordering IT. South West One was a complete administrative and financial disaster area which was high-risk from the word 'go'.

"At least one member of the current cabinet was an enthusiastic supporter of South West One at the time. But the risks of the current proposal are even more obvious.

"The ground work has not been done. It is a potential dive into the expensive unknown by people who ought to know better."

The council's cabinet discussed the new IT system on March 16, with the project cost being estimated at £7.662M – with an additional £1.473M being provided as a contingency if it was needed. The council said the new system was essential to ensuring staff could be paid when the new unitary authority formally takes control – and said leaving a decision until this point could have ultimately cost taxpayers even more.

A council spokesman said: "The new Somerset Council needs to be able to pay its bills, and that means having a single ledger system in place on 1 April 2023. Doing nothing is obviously not an option.

"With the current SCC system at the end of its life, we have worked with our technology partners to select a preferred system that best met the council's needs, Microsoft Dynamics.

"We then carried out a 'discovery phase', working with district colleagues to ensure all needs could be met. That looked two options – one of which was extending the current SAP system for a short term and moving information from the four districts to that system, in the knowledge that the exercise would have to be repeated again the following year as the SAP system came to the end of its life – the 'do it twice' option.

"After substantial review, the preferred option is to move information from five councils to the new Microsoft system in one step.  The risks for both options are broadly similar, but the one-time move to the Microsoft system will be £5.6M cheaper to deliver and save £400,000 in annual running costs, which the new council can invest in front-line services."