Merseyside Police is set to lose about 240 officer posts after authority members backed a recruitment freeze for the foreseeable future.
Merseyside Police Authority approved a moratorium on new recruits until the end of the 2010/11 financial year.
The force was ordered to cut £4.1m from its current budget after the coalition government came to power.
With further cuts of about 25% expected to be imposed, the authority said it faced a "visible effect" on policing.
About 60 officers left the force between April and June and have not been replaced.
The last intake of new officers was in March 2010, but with the force training programme on hold it could be 240 officers down by April 2011.
Merseyside Police Authority (MPA) is awaiting the outcome of the government's comprehensive spending review before making a decision on future recruitment.
According to the MPA report, "those cuts are expected to be in the region of 25% of force budgets over the next four years".
By extrapolating the figures, the Merseyside Police Federation - which represents officers - said the force could face losing up to 1,000 staff over the next four years.
"If we get to that, that means in effect we're going to have to completely reconstruct policing," said spokesman Ian Leyland.
"The service we deliver to the public will not be the one that police officers want to deliver, and not one the public are going to welcome."
Paul Johnson, chief executive of the MPA, said it would be "irresponsible" to restart the recruitment programme until they know the outcome of the government's review.
"Our hope is certainly for the short to medium term we're going to try our very, very best to protect the frontline services that we fought so hard over the last three to four years to reinvest in," he told BBC Radio Merseyside.
"A 25% cut, if that's what transpires, over a period of four years is going to be almost impossible to manage without there being a visible effect on policing in the area."
Mr Johnson said that every effort would be made to protect frontline policing, but that they were "gearing up for the worst".
He added: "What we are doing is trying to take a measured response, put some preparations in place now and hope that through the work that's going on... we can help to cushion as much as possible the impact on front line services."