Your garden backs on to the garden of a neighbour. That neighbour builds a huge extension to the back of his house, and rents it to students, who have frequent loud parties.

What can you do? Not much, under existing planning law. But that is about to change.

The extension may have had planning permission as, say, an extra bathroom and bedrooms. If no one objected and the structure met with planning regulations, then the development is legal. A legal doubt may arise, though, about its use as rental accommodation.

However, your neighbour may be providing tea and toast to the students in the mornings. There is an exemption from planning permission for bed-and-breakfast establishments of less than four rooms.

Even if the extension was built without planning permission, it is difficult for the authorities to move against it.

Their first step would be to seek an enforcement notice in the District Court prohibiting the unauthorised building from being used. Alternatively, the authority can seek an injunction in the Circuit or High Court demanding that it be dismantled. Both routes are strewn with obstacles.

The planning authority must collect evidence that the building is an unauthorised development, or is being used in an unauthorised way. The landlord can frustrate the collection of such evidence in various ways.

Even if the authority gets the enforcement notice, this can be very difficult to implement. The errant landlord can be fined for continuing to use an unauthorised development, but the planning inspectors must prove this by means of five separate visits to the offending property.

The landlord can refuse access, or not turn up for the inspection. Then further court action is required to force the landlord to be present. The whole process can take many months.

Also, financial penalties for breaches of the planning laws are quite low at present.

In one instance, Dublin Corporation prepared a case against a persistent offender and went to court with a huge dossier of breaches of the regulations, including the lack of a fire safety certificate. The landlord was fined £50.

But that is all set to change when the new Planning and Development Act comes into force, a move expected later this year.

In general, the whole enforcement machinery will be more responsive to complaints from members of the public, according to Mr Eamon Galligan BL, who spoke at a recent seminar of the Bar Council on the new legislation.

The planning authorities will be under more pressure to respond to such complaints, and if they decide not to take action, will have to explain this to all those who contact them with bona fide grievances.

An offender will not be able to delay or avoid the implementation of an enforcement notice by making an application for the retention of the unauthorised development.

An enforcement notice will normally be preceded by a warning letter, which can be served on the builder, developer, owner or occupier of the land.

The situation where planning officials turned up and attempted to serve notice on the builders - only to be told that they had no idea who they were working for - will no longer pertain.

Planning officials may enter the land for the purposes of inspection, and the costs associated with all enforcement proceedings may be recovered from the person carrying out the development. This means that obstruction of inspection may turn out to be a costly business.

The penalties for flouting the planning laws are also greatly increased. Conviction on indictment in the Circuit Court can result in a fine of up to £10 million (€12.7m), or up to two years' imprisonment, or both.

A summary conviction in the District Court can result in a fine of up to £1,500 (€1,900), or six months' imprisonment, or both.

There are also bigger penalties for continuing offences - of up to £10,000 (€12,700) a day for each day the offence is continued.

The refusal of a planning authority to issue an enforcement notice, following a legitimate complaint, will now be subject to judicial review.

This means that the aggrieved neighbour, who feels that the planning authority demonstrated inertia, or (rightly or wrongly) was too friendly with the developer, will have some comeback if the complaint was legitimate.

So if you are frustrated by the lack of action on your complaint about your neighbour's extension, wait for the new legislation to come into operation.

Then, if there was no planning permission, action can be taken up to seven years from the time of the development.

If planning permission was in place, the seven-year period applies from the date the permission was issued.