Opposing the closure of three courts, North Lanarkshire council chiefs said the plans would also lead to accused people failing to attend court as they would have to travel for up to an hour to the nearest alternative.
The Scottish Courts Service has recently finished consulting on extensive changes to the way courts operate, from the High Court down.
In all, 11 Sheriff Courts and five Justice of the Peace Courts would shut, with the High Court no longer sitting in Inverness, to save around £5 million a year.
The Law Society has already raised concerns the plans would restrict access to justice, and the Federation of Small Businesses, which has 20,000 members in Scotland, has also said closures will deliver another blow to struggling high streets.
The particular proposals for North Lanarkshire would result in Motherwell, Coatbridge and Cumbernauld Justice of the Peace (JP) Courts closing and their business transferring to Hamilton and Airdrie Sheriff Courts.
In its response to the consultation, North Lanarkshire Council said that, rather than save cash, the proposal would cost the public purse more.
It said the experience of the area's JP courts contradicted the consultation paper's rationale for closure on the grounds of low volume of work, poor facilities and proximity of existing sheriff courts.
As well as "constituting a serious reduction in the availability of the Summary Justice system", the authority said users of Cumbernauld JP Court, because of the wide area it serves, face a journey of up to an hour to Airdrie Sheriff Court.
Its official response states: "Witnesses may find themselves travelling on the same public transport as the accused or witnesses cited by the opposing side.
"Both of these factors will deter witnesses from attending and potentially lead to further delay and expense in securing attendance in court."
Contrary to dwindling business, it said Motherwell JP Court dealt with 2548 complaints last year, up from 2191 in the previous 12 months, adding that transferring business away from local courts will spark a rise in non-attendance and "lead to more warrants being issued to secure accused persons' attendance in court and a greater burden on the public purse".
John O'Hagan, North Lanarkshire's head of corporate services, said: "The council considers that these proposals cause a number of very significant problems.
"Most importantly, they would cause a serious reduction in the availability of justice to many in North Lanarkshire, which flies in the face of the principles on which the summary justice system was founded.
"The council recognises that the Scottish Court Service will have to find savings. But we do not think that cost savings should take priority over access to justice."
A spokesman for the Scottish Court Service said: "An analysis of consultation responses will be carried out during January and February 2013 and we anticipate publishing a report in April 2013 setting out the Scottish Court Service response to the consultation and our firm proposals for future court structures.
"The decision on any resulting court closures would be a matter for the Scottish Parliament and would require the Cabinet Secretary for Justice to bring forward subordinate legislation."