Currently we British do not have a written bill of rights. A bill of rights is considered to be a special set of laws entrenched into the constitution which sets out the rights and freedoms that are enjoyed by every citizen. It is entrenched in the constitution which is vital because it means that it would be far more difficult for the executive to change it (this could be done in a number of ways, for example by making the majority needed for the bill to pass 70% rather than 50+1% for conventional laws).
Currently in the UK we are a long way from this, we don't even have a codified constitution. In theory all British laws are the same. There is no difference between constitutional laws and normal laws, meaning there is no entrenchment and no extra difficulty in changing constitutional laws like there is in all other Western constitutions. So why should we have a bill of rights? One thought behind it is that the current political system, an elective dictatorship, means that all, even basic, human rights could be changed at any time.
The entrenchment of these rights would make them more permanent as well as show citizens what rights the constitution saw as a priority. However this entrenchment is said by those against to go against the organic growth of the UK's current, flexible constitution. Also there would be a huge, almost endless debate as to which laws should be entrenched and which shouldn't. It would even be difficult to decide in what way this bill of rights should be entrenched. Another argument in favour is that a bill of rights would impose real legal limits on the government's actions which are currently only limited by conventions.
How much a government decides to limit its own power at the time will be dubious because of course no government really wants to limit its own power. Surely a bill of rights that takes political power away from the executive and gives it to the judiciary is seen as a bad thing. Many would say it would put too many political decisions in the hands of judges political decisions should rest with the legislature. Judges would also be put in a difficult position because many exiting laws would conflict with a bill of rights.
The rule of law demands a clear, enforceable statement of citizen's rights, a bill of rights would provide this is what many of those who want reform say. However the rule of law contains many dated suggestions and is the judiciary already not enforcing law effectively? Having such an uncompromising bill of rights surely wouldn't promote the evolution of the constitution which the British have enjoyed throughout history. It would possibly be so entrenched that once some constitutional laws became dated, they still couldn't be changed. At least the reliance upon conventions ensures laws that evolve.
Also, the introduction of a bill of rights could lead to a full scale reformation of the constitution; this is what many are hoping for but I along with most others think that this would be wrong. A bill of rights would provide Britain's with a defined mechanism for seeking redress. Currently some cases go to the European Court of Human Rights which is slow and costly. However it could be said that the provision of two courts for people to find justice makes their chance of finding it higher. It also ensures against any corruption as Europe acts as a regulator on the British Judiciary.
A final argument in favour of a bill of rights is that it works well abroad, but the very reason that they have a bill of rights is because they haven't had the opportunity to have the type of constitution we have. Other arguments against are that left-wingers are suspicious of a bill of rights which may entrench right wing principles and vice versa. Good methods for redress already exist. And finally that every bill of rights has a qualifying clause allowing for restriction of rights, as a result some rights acts are useless as they are themselves flexible and inconsistent, the very thing they aim not to be.
If constitutional reform is what people want, there are however various other options. The government could create a department of justice which is itself be accountable and elected into power. This would replace the currently unelected, unaccountable Lord Chancellor's department. The creation of a supreme court, as a last means of appeal, rather than the House of Lords. This would separate the powers and make those in power more impartial and from a wider range of society.
A fourth option is that judges could be elected, making them more representative of society. This however has many problems with it. I however am not so worried about what we shall do to our own constitution, rather what the big guns in Europe shall do if we join the United States of Europe, they will have a bill of rights which having looked at the evidence I am opposed to. If we join Europe, sovereignty will not lie with Westminster or the courts, instead with a commission that is looking out for a whole continent rather than just us.