When you meet someone they take 30 seconds to make up their mind about you - and that first impression can last for up to 15 years, according to psychologists.

Whether it's about meeting clients in a work setting, going for a job interview, or trying to impress the boss for a promotion, it seems that looks really do matter.

Little wonder then that women are prepared to invest more money than ever before on beauty therapy and grooming.

As part of this growing desire to look young and attractive, we splashed out around £1.5 billion on health and beauty treatments last year.

Half of us think it is important to keep young looking, according to research by market analysts Mintel. And six-out-of-ten of us say it is important to look well dressed.

So how crucial is it to a woman's career prospects? Surely it is more important to be able to do your job well than to look great?

Helen Fallon, manager at Reed Accountancy Services in Oxford, has no doubt that appearance does count when it comes to recruitment.

"No matter what the job, it has a massive impact on whether they are going to get the position," she said.

"The biggest factor is whether or not people look as though they have made the effort. It's not down to wearing an Armani suit.

"If someone turns up in a track suit and trainers to an interview with me I just can't help feeling that they are not taking the position very seriously at all."

Tracy Hoodless, founder of Champion Recruitment in Oxford, agrees. "Employers like to see people who look reasonably well groomed."

Angela Scott-Smith is an image consultant for Colour Me Beautiful who has helped hundreds of women update and improve their appearance. She has no doubt that the way you look is absolutely crucial to how you are perceived by your superiors, clients and colleagues at work.

"If you bite your nails or they are disgustingly dirty or you haven't had time to wash your hair it comes across that you don't care about yourself. And if you don't care about yourself, perhaps you won't care about your work.

"Personal hygiene and appearance are so important. People make judgements about you and they are often based on instinct rather than logic," she explained.

The degree to which your look matters does depend on the role and the type of organisation you are applying to, according to Tracy Hoodless.

"If they are going for an interview as a receptionist, which is a front of house job, you would expect them to look smart and tidy. That would be quite important."

"But it's a fairly good rule that you should look clean, smart and tidy whatever post you are applying for," she added.

Dressing to impress can have other, more subtle benefits, believes Angela Scott Smith. "You have really got to think about what you are wearing," she pointed out.

"If you know you look good your body language is more positive when you feel great it comes across via better eye contact and you sound more confident."

And if you're under the impression that little things don't matter, think again. According to Helen Fallon, one of the most common criticisms she hears from potential employers is that they notice - and are unimpressed - when a candidate goes for an interview wearing dirty shoes.

Helen has been working in the recruitment business for 12 years and during that time she believes standards have slipped. "People think nothing of presenting themselves at an interview wearing jeans or track suit tops or bottoms or trainers. I see more and more of that. Some go dressed as though they are sunbathing in the back garden."

And others are not averse to pulling out all the stops for an interview, then letting themselves go once they are in the job.

"For any job where you are dealing with members of the public or clients you can train somebody to say the right things and teach them all the skills they need. But they have got to have the natural ability to want to look smart for day-to-day work," added Helen.

But it isn't all the employee's fault, according to Helen. Employers are far more relaxed about dressing for work and many have introduced dress down' days where employees are encouraged to go into the office wearing jeans or other casual gear.

"The fine line between business and casual wear is blurring," Helen added. "Once, everyone knew it wasn't suitable to wear peep toe shoes, low cut tops or no tights to work whereas now, if you walk into any office, you see people wearing sandals and jeans."

Tracy Hoodless has had experience of an employer being impressed with a person's skills but less so with their appearance: "A candidate went along to a bank and wore jeans and the employer said this person is very good at what they do but could you remind them that they are not going to a rodeo?'.

"If you go into a bank you won't see anyone working there wearing denims so it is a good idea to wear appropriate clothing, depending on the profession and the type of business," she said.

Employers choose candidates who they think will fit into their organisation and according to Angela Scott Smith that includes the way you present yourself visually.

She advises going along a few days before your interview at lunchtime or the end of the working day and watching people who work there as they come in and out of the building to see what they are wearing.

This will give you visual clues as to how you can present yourself to literally look the part.

"You have got to fit in visually. All of us like and are attracted to other people who look like us," said Angela.

But it's not rocket science, according to Helen Fallon: "I think it's just common sense a lot of the time. In a working environment you are supposed to be there to work, not dressed to go straight to the pub at 5.30pm.