The article examines the effectiveness of one technique of grassroots lobbying (e-petitions) in the UK through the prism of: (1) the claim that the goal of lobbying activity (the change versus protection of the status quo policy) is a great predictor of lobbying’s outcome; (2) the signalling theory; (3) the amended version of the economic theory of political information. In the paper, I studied the petitions signed by at least 10,000 citizens submitted to the House of Commons during the 57th Parliament of the UK (2017–2019) and analysed their effectiveness. I also measured the petitions’ issue salience for the ruling party (the Conservative Party) from the perspective of the analysed theories. The research results indicate the following: (1) e-petitions aiming to defend the status quo policy were considerably more effective than the ones striving to change it; (2) the scale of e-petition’s endorsement was not a crucial factor in determining the authorities’ decision, contradicting the assumption of the signalling theory; (3) moderately and highly popular lower salience issue e-petitions showed equal ineffectiveness. On the other hand, greatly popular higher salience issue e-petitions supported by the ruling party were less effective than their less popular counterparts. Conversely, e-petitions on higher salience issues opposed by the ruling party, whether moderately or widely endorsed by the public, exhibited equal ineffectiveness. These results mean that the economic theory of political information only partially explains the effectiveness of grassroots lobbying (i.e. in the last case). In conclusion, e-petitions represent a relatively efficient grassroots lobbying technique for influencing authorities in the UK, with approximately one in five being considered effective.