County governments have been instructed to stop monthly subscription fees to the Kenya National Union of Nurses until verification of every member is done.
According to a letter signed by the Council of Governors chairman Josphat Nanok, authentication must be done by individual nurses within 90 days.
"The Council of Governors maintains that the union must demonstrate proof of compliance with the recognition agreement...before member subscriptions are remitted," Mr Nanok said.
Governors insist that the ongoing nurses strike is illegal.
However, the union threatened to sue the governors.
It said stoppage of monthly subscriptions was a desperate measure aimed at intimidating it and the members.
"We wish to remind you that the right of an employee to belong to a union is anchored in the Constitution," union Secretary-General Seth Panyako said.
Mr Panyako added that while recruiting members, the union adhered to the Labour Relations Act.
His sentiments were echoed by the union's acting chairman Joseph Ngwasi.
"Nanok cannot stop the deductions because the law governing the registration and membership of nurses is clear," Mr Ngwasi said by phone.