No, employers are prohibited from making an offer to employees which is designed to induce them:
not to be (or seek to be) a member of an independent trade union;
not to take part in the activities of an independent trade union, either in their own time or in work time where allowed;
not to make use of trade union services, either in their own time or in work time where allowed; and
to become a member of any union, or of one particular union.
Employers are also banned from offering an inducement to a member of a trade union that is recognised or seeking recognition to stop or prevent their terms and conditions being negotiated collectively (i.e. through collective bargaining).
An example would be where an employer offers each employee a one-off cash bonus in return for switching from collectively agreed terms to an individual contract of employment.
The compensation due from the employer to each member who has been offered this kind of inducement is £4,294 (April 2020).