The East Midlands regional branch of Unite has claimed that "penny pinching" council bosses have removed specialist elements from Level 1 training.
They say this means that the workers are health visitors in name only.
The changes, brought in after the professionals transferred from the NHS to the local authority in October 2017, mean that leadership, planning, evaluating and managing complex safeguarding skills are now only included at Level 2.
Some 57 health visitors are being balloted on strike action over demands for a payrise in line with the county council's grade 10, which the union is calling to be backdated to April last year.
Unite regional officer Steve Syson said: "We also want no reduction in our members' professional responsibilities and duties."
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Unite professional officer for the East Midlands Jane Beach said this created a "two-tier health visitor service that is being dressed up as a so-called 'career progression scheme'".
"By removing the specialist elements, the Level 1 no longer constitutes a health visitor role," she said.
"This will leave a big gap in the service putting children and families at risk with fewer Level 2 health visitors who themselves will be at risk of burnout."
Beach branded the move "short-sighted" adding that it will result in delays in support for children and families in Lincolnshire.
She said that many are vulnerable and could suffer a "serious impact on their health and social welfare".
Sally Savage, assistant director of children's services at the county council, disputed the claims, insisting that health visitors - who are qualified nurses and midwives, are a "valued part of our workforce".
"We don't agree with Unite's assertion that the county council have reduced the professional responsibilities and duties of health visitors, who are a valued part of our workforce, using their professional skills on a day-to-day basis to support children and their families."
The ballot closes on 27 June and the dispute involves 57 health visitors who were transferred from the NHS under Agenda for Change terms.
There are 111 full-time equivalent health visitor posts in the council - and the others are either on grade 10 contracts or began their employment after October 2017. There are also some student health visitors.
Unite has calculated that members have lost more than £2,000 a year since the transfer.
The health visitors are on NHS Agenda for Change pay scales but have had no increases in pay since being transferred to the local authority, which has different pay rates.
Even though council and NHS employees have received wage awards, these health visitors have not.
Savage said that to "enable health visitors to continue to receive inflationary increases in their salaries, all have been offered an opportunity to transfer to the county council terms and conditions, whilst retaining their NHS pension."
She added that the council's pay scales are slightly higher than that of Agenda for Change.
"We feel that this offers a proportionate response to Unite's concerns," she said.
"We have invited Unite to submit a formal dispute so that we can sit round the table with them and explore how we can resolve this issue, but to date, they have not submitted a dispute.
"We are working with the other unions who are supportive of our position."
Dr Cheryll Adams, executive director of the Institute of Health Visiting, called for government to set "robust national standards" for commissioning, adding that the same terms and conditions should be used as with the NHS.
Adams compared the situation to that of Scotland, where she said health visitors are paid fairly.
Adams said: "I am very sad that in three short years the health visiting service has been so decimated by cuts to public health budgets and local decision making that health visitors now find themselves having to strike to try maintain the Agenda for Change salary level which reflects their level of skills and expertise.
"They are advanced specialist nurses with a portfolio of high-level skills. How distressing it must be to find themselves being treated as newly trained nurses on the pay scales.
"The model of moving health visiting commissioning to local authorities accompanied by cuts to public health budgets has been a significant challenge to the profession.
"We now have not only a health visitor workforce already depleted by 25 per cent with the risk of more cuts, but also wide variations in commissioning decisions around the country resulting in a postcode lottery in access to the health visiting service."