Removing half of councillors, saving £21 million per year and the "logical option" of joining the West Midlands Combined Authority form part of Warwickshire County Council plans for a new unitary authority.

Councillors on the county's cabinet – the Conservative panel in charge of decision making – will discuss a 26-page draft rationale for one new county-wide council to deliver services currently divided over two levels of local government on Thursday. 

It acknowledges throughout the counter proposals for two unitaries – one covering Warwick and Stratford districts, the other covering Rugby, North Warwickshire and Nuneaton and Bedworth – but strongly makes the case for one county-wide body. 

The initial submission must go to the government by March 21 with detailed proposals to be fleshed out by November. The cabinet will be asked to vote to allow leader Cllr Izzi Seccombe and chief executive Monica Fogarty to file Warwickshire's plan in line with the rationale. 

It is argued that keeping together services delivered by the county council, including social care and education, or on a county-wide basis such as fire and police, would be more cost effective than pulling them apart or placing them into county-wide trusts across two council patches. 

The differences between the north and south are highlighted with the northern three boroughs making up 52 per cent of the population but only 46 per cent of the council tax base, matters exacerbated by the north having 21 of the county's 22 most deprived areas.

The six current councils combined have savings targets of £30.1 million per year, rising to £97.8 million five years from now. The county's early estimates suggest £21 million per year could be saved by one council, adding that the figure comes down to £7 million if there are two unitaries.

The county also says that extra costs to divide up county-wide services mean only £8 million would be saved in the first five years across two authorities with £82 million to be saved by just one.

One number that plummets under either model is the number of elected councillors. As things stand, there are 257 seats across the six councils, and while some are held by 'twin-hatters' – councillors serving at both levels – the county expects there to be between 80 and 120 seats on a single council or 100 and 128 across two. 

Much is made of the existing relationship, particularly economically, with Coventry and it is made clear that the city council is "not seeking to leave the West Midlands Combined Authority (WMCA) to form another arrangement". 

Coventry is a full member whereas each Warwickshire council is a non-constituent member with less power but also less financial obligation. 

The report highlights economic benefits such as the Coventry & Warwickshire Gigapark in Warwick district, adding: "Full membership of the West Midlands Combined Authority appears the logical option in terms of maintaining the critical Coventry and Warwickshire economic geography, driving housing delivery and addressing climate change. 

"At the same time, it would enable Warwickshire to access the fullest suite of devolution benefits."

It concludes that "this would require consent of the new Warwickshire council or councils, the (West Midlands) mayor and the secretary of state".