There is not a straightforward answer to this question. The Equality Act 2010 protects you against discrimination on the grounds of marital status (i.e. where you are treated less favourably because you are married or unmarried). It gives the same protection to people in a civil partnership.
However, the tribunal case law is contradictory and there are cases that suggest that it is the status of marriage that counts, not who you are married to. For example it would be 'marriage discrimination' for your employer to refuse to employ you because of a belief that married employees are more likely to start a family than unmarried employees. That is not the same as treating you differently because you are married to a particular person (i.e. your husband – an existing employee).
It would be sex discrimination if the company would have treated a male employee differently. Refusing you the job could also contravene the Human Rights Act, which allows you a right to a private life and family life.
Get advice from your or your spouse's union, if either of you are union members. A union may well be able to persuade the company to consider your job application fairly, without you having to go to the expense of involving a lawyer. There may be practical suggestions you can make. For example, you could offer to work in a different team, department or location.