An example of a Departmental select committee operating in the past is when they sternly questioned David Kelly about the weapons of mass destruction, and also when they questioned the former bosses of HBOS and RBS. This demonstrates how they have worked properly before, which repels the “toothless” statement.
However, one could say that they are ineffective. This may be due to a number of reasons, one of which could be that they don't actually have any power to propose policy or to change anything- the government can simply ignore them. This shows that if they can't, on their own, create and implement a policy, then they are simply nothing more than powerless advisers. On top of that, they don't have a complete access to documents, as the government may deny them the right to look at certain documents. Also, the membership of the committees is heavily influenced by whips, who try their best to choose the MP's of their own choice to put on committees, and who also try to remove committee chairs who are independent, as whips disprove of this. In the past there have also been instances of committee chairs causing problems- in 2001 the Labour government failed to remove their own MP after a rebellion in their own ranks. This shows that committees can at times cause unwanted trouble within the government and can destruct, instead of construct- something which is not at all useful and can make some people see them as nothing but a hindrance to the government. The committees may also be seen by some as impractical and unfair, as a government with a majority in the House of Commons will also have a majority in the committees, which does not fairly represent members of opposition parties and could make them less efficient
In conclusion, I believe that departmental select committees can at times prove to be ineffective and even useless, though on the whole they are an essential part of today's parliament and are necessary to keep the government in order.