Hertfordshire County Council has formally asked the Government to disclose the evidence behind its decision to replace the county's existing councils with four new unitary authorities.

The county council has issued a Pre-Action Protocol letter to the Secretary of State for Housing, Communities and Local Government following the Government's decision on Local Government Reorganisation (LGR) in Hertfordshire.

The move could potentially precede a legal challenge, although the council has stressed that it has not decided to pursue a judicial review and is not seeking to stop the reorganisation.

Under the Government's plans, Hertfordshire's existing county, district and borough councils – including North Herts Council – are due to be replaced by four unitary councils as part of the biggest shake-up of local government in the county for decades.

Hertfordshire County Council had previously backed an alternative proposal based around two unitary authorities.

Following a motion agreed by the full county council in July, independent legal advice has now been taken and the authority has formally requested information about how the Government reached its decision.

It is seeking the evidence, analysis and financial assessments used by ministers, particularly those relating to the financial sustainability of the new authorities, the implications of the Fair Funding Review and population sizes.

The council says it took the step after receiving no substantive response to repeated requests for further information from the Ministry of Housing, Communities and Local Government since the end of July.

A Pre-Action Protocol letter allows an organisation to seek information and explanations before deciding whether to pursue legal proceedings.

Councillor Steve Jarvis, Leader of Hertfordshire County Council, said the authority had taken the step "reluctantly".

He said the council remained concerned that the four-unitary model represented "the most expensive, complex and disruptive option for Hertfordshire".

Cllr Jarvis also pointed to the Government's consultation analysis, which he said showed the two-unitary proposal was the most popular option among respondents overall, Hertfordshire residents and key partner organisations.

He added: "The changes proposed are the biggest transformation of local government in Hertfordshire for 60 years and will have an impact for decades to come so it is vital that decisions are based on robust evidence and sound financial analysis in the best interests of our county.

"We will carefully consider the Government's response and consider what, if any, further action is appropriate."

Despite the move, the county council says it will continue working with the Government, Hertfordshire's district and borough councils and other organisations to prepare for the introduction of the new local government arrangements in 2028.

The authority also says it will continue pushing for further devolution, including the creation of a mayor for Hertfordshire.