He was opposed by the Duke of Clarence, who directed his remarks chiefly to a defence of the general humanity of the planters; and by Lord Westmoreland, who, in a speech of singular intemperance, denounced the principle of the measure, as one after the passing of which "no property could be rendered safe which could fall within the power of the Legislature." He even made it an argument against the bill that its principle, if carried to its legitimate logical end, must tend to the abolition of slavery as well as of the slave-trade.

He objected especially to the assertion in the preamble that the trade was "contrary to justice and humanity," declaring that those words were only inserted in the hope that by them "foreign powers might be humbugged into a concurrence with the abolition," and wound up his harangue by a declaration that, though he should "see the Presbyterian and the prelate, the Methodist and pew-preacher, the Jacobin and the murderer, unite in support of it, he would still raise his voice against it." It must have been more painful to the minister to be opposed by so distinguished an officer as Lord St.
Vincent, who resisted the bill chiefly on the ground that "its effect would be to transfer British capital to other countries, which would not be disposed to abandon so productive a trade," and declared that he could only account for Lord Grenville's advocacy of it "by supposing that some Obi man had cast his spell upon him." But the case was too strong for any arguments to prevail which were based solely on the profits of a trade which no one pretended to justify.

The bill passed the Lords by a majority of nearly three to one; in the House of Commons, where the opposition was much feebler, by one infinitely larger;[161] and, by a somewhat remarkable coincidence, it received the royal assent on the same day on which Lord Grenville announced to his brother peers that his administration was at an end.
Even before the abolition had thus become law, the member for Northumberland, Earl Percy, endeavored to give practical effect to Lord Westmoreland's view, that emancipation of the slaves was its inevitable corollary, by moving for leave to bring in a bill for the gradual abolition of slavery in the British settlements of the West Indies.

But he was opposed by Lord Howick,[162] though he had been among the earnest advocates of abolition, partly for the sake of the negroes themselves, and partly on the ground that the Legislature had no "right to interfere with the property of the colonists;" little foreseeing that the measure which he now opposed was reserved for his own administration, and that its accomplishment would be one of its chief titles to the respectful recollection of posterity.

And, as the House was presently counted out, the discussion would not have been worth recording, were it not for the opportunity which it gave of displaying the practical and moderate wisdom of Wilberforce himself, who joined in the opposition to Lord Percy's motion.