In most cases, we would always suggest smart business dress.

Business suit, shirt and tie for men and smart, appropriate clothing for women.
Clean, appropriate shoes are important too, as they help to complete the look.

Sometimes smart trousers, shirt and tie suffice instead of
the suit – particularly in companies where business dress is not the norm.
Manual workers, trades and labour should still make a good impression by
considering how they dress for their interview, rather than showing up in everyday
work gear.

However, there are some times when it’s not possible to do
that. If getting time off for an interview is difficult, it may be that you
need to go before or after work, which would mean you are in your working
clothes. A manual worker might get a few strange looks if they turned up to
work ready for a later interview, dressed in smart business attire! So it’s
important to manage expectations. If you DO have to go straight from work, ask
beforehand if it’s ok to turn up in your work clothes. Most times you will find
it’s perfectly acceptable, so long as the interviewer knows before-hand.

Conversely, you might have an interview on a day where the
company who are recruiting have a ‘dress down’ day. So the interviewer might
pre-warn you and invite you to dress more comfortably so that you don’t feel
out of place when you arrive.

So in a nutshell just think about the image that you
project. Make sure the clothes that you wear to the interview are appropriate
for the role and the style of interview. Check that they say you really want the
job and are prepared to make an effort. If you are applying through a
recruitment business, ask your consultant – they will be familiar with the
client. They can advise you and also liaise with the client if you do find yourself
having to go straight from work in your work gear.