This is a common issue in the present climate. The first thing to look at in these circumstances is whether or not this is a short term problem.
If it is then you could look to "lay off" your employees, provided that you have the contractual right to do so. The right to lay off should be detailed in either the contract of employment or an employee handbook. In the absence of this, you do not have the right to impose lay off.
Provided you do have the right, then you can choose whom to place on lay off, it does not have to be as formal as a redundancy selection. Ideally, give the employee some notice of this, but it is accepted that this is not always possible to do. Employees on lay off are entitled to guarantee pay (currently £21.50 per day) for the first 5 days in any period of lay off.
You should give the employee a letter to confirm this, in order that they can take this to the Job Centre to see if they are eligible to claim any other benefits.
If the period of lay off goes on for a period of 4 weeks or more, the employee can give their written notice and claim a redundancy payment from you. You can refuse to meet the claim and serve counter notice that within 7 days you can reasonably expect to provide at least 13 weeks continuous employment without further resort to lay off.
If you do not have the contractual right to lay off, you can try to seek the employees' agreement to do this. If the employees do not agree to this, or if this is a long term problem, then unfortunately it is highly likely that voluntary or compulsory redundancy will be the way forward.