No one knows more about your shopping rights than Mary Portas, style legend and presenter of the Channel 4 show Mary Portas: Secret Shopper. She shared her tips on the best way to return a dodgy purchase and get your money back.

1. Don't Suffer in Silence

Many of us hate complaining, but it's important that you make yourself heard if you are not happy, says Mary.

'Service should match the quality of the goods on sale and the environment in which they are sold,' she says. 'To serve someone well requires skill, and is a profession. But here, unlike America or Italy for example, it is not considered so. The consequences can be shoddy, and they won't get better unless shoppers vote with their wallets, and let the people at the top know that they're not happy.

'Making a complaint is not very British. We may mutter under our breath, hold grudges and opt to keep the useless item of clothing rather than have to suffer a till tirade, but complaining is the only way if you're not getting the service that you expect.'

2. Introduce Yourself

'It's all too easy to get bolshie with sales assistants,' says Mary. 'But venting anger and frustration may not help your cause. Being communicative will. Smile a lot, look the person you are dealing with in the eye and address them by name (if they're not wearing a badge, tell them your name and ask theirs). Use their name next time you are in store, and you'll have more success in getting good service.'

3. Keep Your Cool

'Making a complaint requires a mixture of will, charm, politeness and diplomacy. Don't go storming in demanding to see the manager - respect that the sales assistant has the authority to act on the store's behalf. Be calm and to the point and make sure you take the faulty goods, any packaging and the proof of purchase with you.

'If you still meet resistance and have exhausted all options with the sales assistant, state politely that you would like to seek a resolution to the situation and ask to see the manager.'

And finally: Know your rights, don't delay to check your purchases and act quickly if there's a fault. If you're not getting the service you deserve - don't buy from that shop again.